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Article

Temperature and Nutrient Effects on Organic Exudate Production in Lingulaulax polyedra (Stein) Head et al., 2024 Cultures

by
Rigel Castañeda-Quezada
1,
Mary Carmen Ruiz-de la Torre
1,*,
Guillermo Samperio-Ramos
2,
Ernesto García-Mendoza
3 and
Miguel Matus-Hernández
3
1
Facultad de Ciencias Marinas, Universidad Autónoma de Baja California (UABC), Carretera Transpeninsular Ensenada-Tijuana No. 3917, Ensenada 22860, Mexico
2
Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California (UABC), Carretera Transpeninsular Ensenada-Tijuana No. 3917, Ensenada 22860, Mexico
3
Departamento de Oceanografía Biológica, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Ensenada-Tijuana #3918, Ensenada 22860, Mexico
*
Author to whom correspondence should be addressed.
Phycology 2025, 5(3), 42; https://doi.org/10.3390/phycology5030042
Submission received: 2 June 2025 / Revised: 4 August 2025 / Accepted: 26 August 2025 / Published: 2 September 2025
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Abstract

Transparent Exopolymer Particles (TEP) play a key role in the marine carbon cycle, facilitating the aggregation and exportation of organic matter. TEP production is particularly relevant during Harmful Algal Blooms (HABs), where dinoflagellates like Lingulaulax polyedra can release significant amounts of exudates. Temperature is a crucial environmental factor that influences HAB dynamics and physiological processes of bloom-forming species, affecting exudate composition and abundance. This study investigates the influence of temperature and nutrient availability on the production of organic exudates in L. polyedra cultures. TEP, Particulate Organic Carbon (POC), and Particulate Organic Nitrogen (PON) concentrations were analyzed under controlled laboratory conditions. Batch cultures were maintained at temperatures of 17, 20, and 25 °C, with two nutrient regimes (low and high nitrate and phosphate concentrations). Exudates were quantified using colorimetric and spectrophotometric methods. We found that temperature and nutrient availability significantly influence exudate production. The highest TEP concentration was recorded at 25 °C in cells cultivated under low-nutrient conditions, whereas POC exhibited a notable increase at 20 °C. ANOVA revealed that TEP and POC were the primary drivers of variability among treatments. These findings reveal that temperature is important in the regulation of L. polyedra exudate production. The role of this variable on organic matter cycling and bloom dynamics in marine ecosystems is discussed.

1. Introduction

Particulate and colloidal organic matter have different origins and sizes and play fundamental biogeochemical and ecological roles in the ocean. Microorganisms within the microbial loop consume this organic matter and can be exported to the deep ocean through the biological carbon pump, a key component of the global carbon cycle [1,2,3,4].
Microgels are important components of marine particulate and colloidal organic matter. The formation of marine microgels begins with the aggregation of high molecular weight polymeric precursors smaller than ~0.4 μm [5]. These polymers primarily consist of anionic colloids rich in acidic polysaccharides and amphiphilic protein chains [5,6]. Exopolymers released by bacteria and phytoplankton constitute one of the main reservoirs of marine macromolecular organic carbon [7]. These exopolymers self-assemble through hydrophobic cross-linking interactions with low-energy bonds, followed by coagulation and gelation mechanisms [8]. Consequently, marine microgels are categorized as either transparent exopolymer particles (TEP) if they are carbohydrate-rich or Coomassie stainable particles (CSP) if primarily composed of proteins [4,9]. The nonlinear behavior and structurally dynamic nature of TEP are responsible for the position of these aggregates as a transition between the dissolved organic carbon (DOC) pool and particulate organic carbon (POC). Understanding the factors that influence TEP formation is essential for elucidating oceanic carbon cycling.
Dinoflagellates are important components of coastal phytoplankton communities, are a diverse group of unicellular protists, widely distributed in marine and freshwater environments. They are characterized by two perpendicular flagella that give them a distinctive spinning motion, and a complex cell structure that in many cases includes cellulose plates forming a theca [10,11]. Many dinoflagellates are photosynthetic and contribute significantly to primary productivity in coastal ecosystems, although heterotrophic and mixotrophic forms also exist [12]. They are distributed worldwide, with greater abundance in temperate and tropical zones, and several species are known to form algal blooms, some of which can be harmful to marine biota and human health [13]. These organisms are potential producers of TEP precursors [14,15]. In coastal waters of New Zealand, dinoflagellates such as Gonyaulax hyalina have been identified as significant exopolymer producers [16]. The highest recorded TEP concentrations (~17 mg Xeq L−1) have been reported in monospecific cultures of Lepidodinium chlorophorum [17]. This production harmed the growth of the dinoflagellate associated with the presence of bacteria. Though it has been demonstrated that dinoflagellates produce TEPs, it is not known how the environmental variables affect exopolymer production in this group of microalgae.
Temperature and nutrient concentration are environmental variables that regulate the population dynamics of bloom-forming dinoflagellates and affect exopolymer release rates and molecular composition [18,19,20,21]. Temperature is particularly crucial since it influences dinoflagellate growth, photosynthetic activity, and carbon pool allocation, thereby promoting dissolved organic carbon (DOC) exudation [22]. On the other hand, nutrient stress has been proposed as a driver of TEP precursor production due to intracellular carbon and nutrient metabolism imbalances [23]. However, laboratory studies indicate that exopolymer production is highly species-specific and depends on the physiological state of cells [24].
Lingulaulax polyedra frequently proliferates in coastal upwelling zones associated with eastern boundary upwelling systems [25,26] and forms frequent and dense blooms in the southern part of the California Current System. The environmental conditions that induce TEP formation in this species have not been documented. This study aims to assess the exudation rate and TEP released by L. polyedra under controlled culture conditions with varying nutrient availability and temperature. To improve our understanding of ocean warming and its consequences, cells were cultured at 17, 20, and 25 °C. In Todos Santos Bay (Ensenada, Baja California), the average surface temperature is 17 °C, reaching highs of up to 21 °C during the summer [27]. Therefore, the 25 °C condition was selected as an elevated temperature outside the normal natural range, to simulate thermal stress scenarios that could occur under climate change conditions. TEP concentrations were compared with particulate organic carbon (POC) and nitrogen (PON) to determine their relationships under different experimental conditions.

2. Materials and Methods

2.1. Experiments with Monoclonal Cultures of Lingulaulax polyedra

L. polyedra was isolated from samples collected in Todos Santos Bay, Ensenada, Mexico, by the Laboratory of Marine Microbes and Harmful Algal Bloom Ecology of the Faculty of Marine Sciences, UABC. Live samples were obtained using a Niskin bottle (5 L, General Oceanics). The culture was established in 250 mL flasks under controlled conditions at 20 °C, with a light-dark cycle (12:12) at an irradiance of 160 μmol photons m−2 s−1, using F2 medium [28,29] (for details of F2 medium formula, see Table A1, Appendix A).
The observation of live and fixed cells was performed using an inverted microscope (DM13000 B Leica, Wetzlar, Germany) and a compound microscope (DM3000 Leica, Wetzlar, Germany). The samples were fixed with neutral lugol at a final concentration of 1%. For detailed morphological analysis of the thecal plates of L. polyedra, fixed cells and observations under optical microscopy were used. The images were obtained with a digital camera Flexacam C3 Leica, Wetzlar, Germany (see Figure 1).
The morphological identification of L. polyedra was carried out through microscopic observation at a magnification range between 40× and 1000×, evaluating key taxonomic characteristics such as cell shape and symmetry, flagellum arrangement (transverse and longitudinal), the pattern of the thecal plates, and cell size. Cell length and width measurements were performed at 1000× magnification on freshly fixed cells selected from late exponential phase cultures with high density and healthy morphology, previously verified by stereomicroscopic inspection of the live material. Taxonomic determination was based on recognized reference works [10,30,31], which include illustrated keys and detailed descriptions of the characteristic thallus structures of this dinoflagellate.
The temperature at the time of isolation of L. polyedra was 17 °C. The proliferation of this species is usually documented between 17 °C to 20 °C [32,33]. Both temperatures were considered as cultured conditions, and cells were also grown at 25 °C. This condition was considered as extreme or stressful temperature. At each growth temperature condition (17, 20, and 25 °C), cells were exposed to two nutrient regimes. Low nutrient (LN) and High (HN) regime as shown in Table 1.
Three cultures were established at each condition (17, 20, and 25 °C), in a culture incubator with constant temperature (±0.5 °C), automated irradiance, light/dark hours, and a sterile environment, model VWRTM BOD (USA). The acclimatization of L. polyedra at each culture condition was considered complete after three complete cycles of cell division, monitored by microscopy, growth curve, and stabilization of the growth rate at each temperature condition. Cell abundance was monitored once every three days using a Sedwick-Rafter cell, and aliquots were fixed with concentrated Lugol-Acetate solution. Cell counts were conducted in triplicate using a light microscope (DM3000 Leica, Wetzlar, Germany). The growth rate (μ) was calculated during the exponential growth phase based on the regression equation between the natural logarithm (ln) of cell abundance and time [34]. Samples were collected at the stationary phase of growth for the determination of TEP, POC, and PON.

2.2. Determination of Exuded Material (TEP, POC, and PON)

50 mL were filtered through 0.45 μm pore size polycarbonate filters (Nuclepore, Whatman, Marlborough, MA, USA, 25 mm) for TEP analysis. For POC and PON also, 50 mL of algal culture was filtered through a combusted glass fiber filters (0.7 µm pore size, heated to 450 °C for 4 h). The membrane was then wrapped in aluminum foil, dried at 40 °C for 48 h, and stored at −20 °C.
TEP quantification was performed using a colorimetric method [35]. One milliliter of alcian solution (0.02% in 0.06% acetic acid, pH 2) was filtered through the filters, ensuring complete coverage, followed by rinsing with Milli-Q® water to remove excess dye. Blank filters were measured following the same staining protocol. The filters were placed in 80% sulfuric acid (H2SO4) for extraction. The absorbance was measured at 787 nm using a Lambda 40 UV/VIS spectrophotometer (Perkin Elmer, Waltham, MA, USA). TEP concentrations were quantified based on a calibration curve constructed using xanthan gum as a reference standard and were generated according to Bittar et al. [36]. Final concentrations were calculated using the equation proposed by Villacorte et al. [35] and are expressed in micrograms of xanthan gum equivalents per liter (μg-XG L−1), reflecting the amount of TEP relative to an equivalent xanthan gum concentration.
To measure Particulate Organic Carbon and Nitrogen (POC, PON) content, a 5 mol/L hydrochloric acid solution was used to wash the filter and was dried at 40 °C for 48 h. The dried membrane was loaded into an aluminum cartridge, and samples were analyzed in a Simultaneous Carbon, Hydrogen, and Nitrogen Analyzer (Vario Micro Cube, Elementar. Langenselbold, Germany) operating in CHN mode. Subsequently, the concentration of POC and PON (μmol·L−1) was determined in the samples based on the areas of their peaks in the chromatograms and the calibration obtained from the number of moles of carbon (nitrogen) (α and β, respectively) present in different concentrations of an acetanilide standard and as a function of the filtered sample volume. Similarly, the carbon ratio was calculated. The carbon-nitrogen (C/N) ratio (mol/mol−1) was also calculated for each sample.
Concentrations were normalized by cell abundance to obtain data per cell (μg-XG cell−1, mg cell−1), which allowed patterns to be identified beyond the effect of biomass.

2.3. Statistical Data Analysis

To apply an ANOVA analysis, the homogeneity of variance (homoskedasticity results of the data were evaluated using Levene’s test) and the Shapiro-Wilk test for normal distribution. In case the assumptions were not met, the Kruskal-Wallis test, with Dunn’s post hoc test [37], was applied under Bonferroni’s correction.
A two-way PERMANOVA and Tukey’s post-hoc tests were conducted to evaluate the impact of nutrient and temperature treatments on TEP, POC, PON, cell abundance, and the interaction between factors. And one-way ANOVA to assess the interaction independently, and a main effect of each factor, with temperature and nutrients. The SIMPER test with the Bray-Curtis distance was employed to quantify the contribution of these factors using the software PAST v4.10 [38]. The significance level was 0.05, and all graphs show standard error bars calculated on three independent biological replicates were used per experimental condition (n = 3) and three technical replicates per sample.

3. Results

3.1. Temperature and Nutrients (NO3, PO4) Effects on the Growth of L. polyedra Cultures

Cellular abundance dynamics of L. polyedra varied with temperature, particularly under a low nutrient (LN) regime. During the initial 18 days of cultivation, homogeneous growth and cell density were observed across all temperatures (17, 20, and 25 °C). However, after this period, and notably by day 21, an increase in cell abundance was detected in cultures maintained at 25 °C and 17 °C. In contrast, cultures at 20 °C exhibited a slower growth in their cell abundance. The highest cell abundance was recorded in cultures at 25 °C, reaching a density of 14,040 cells mL−1 by day 27 (Figure 2).
Further analysis of the growth curves revealed distinct patterns across the tested temperatures. The culture maintained at 17 °C exhibited a relatively short exponential phase, ultimately reaching a maximum density of 9283 cells mL−1. In contrast, the culture at 20 °C displayed the most anomalous behavior; its growth during the exponential phase was the slowest among the three temperatures, and it achieved the lowest maximum cell concentration of 7303 cells mL−1. Under low nutrient (LN) conditions, the culture maintained at 25 °C consistently showed the highest cell density, as noted previously.
The specific growth rates (μ), calculated during the exponential phase and expressed in days (d−1), corroborated these observations (Table 2). The highest specific growth rate was recorded at 25 °C (0.45 d−1), followed by 17 °C (0.42 d−1). The lowest specific growth rate was observed at 20 °C (0.37 d−1), reinforcing the atypical growth pattern at this temperature.
The cultures maintained under high nutrient (HN) concentrations exhibited consistent growth phase development across all three temperatures. At 20 °C, the culture showed constant growth, reaching a population of 7766 cells mL−1 by day 27, with a slightly higher specific growth rate of 0.38 d−1 compared to cultures under LN conditions. Similarly, the culture at 17 °C displayed a slight exponential phase between days 21 and 27, achieving 8670 cells mL−1, although its specific growth rate showed a slight decrease to 0.41 d−1. In this HN experiment, the culture maintained at 25 °C exhibited the most pronounced exponential phase, spanning from day 21 to 27, with a specific growth rate of 0.43 d−1. This culture reached a maximum cell concentration of 11,000 cells mL−1 before entering a decay phase.
At 17 °C, the culture with low nutrients (LN) reached the highest cell concentration of 9283 cells mL−1, slightly surpassing the 8670 cells mL−1 recorded in the high nutrient (HN) condition. Despite this difference in abundance, the specific growth rates were similar in both treatments, at 0.42 d−1 (LN) and 0.41 d−1 (HN).
At 20 °C, the specific growth rate remained consistent, with values of 0.37 d−1 (LN) and 0.38 d−1 (HN). The final cell concentrations at the end of the exponential phase were also comparable, reaching 7766 cells mL−1 in HN and 7920 cells mL−1 in LN.
The highest growth performance was observed at 25 °C. In this treatment, specific growth rates reached 0.45 d−1 with LN and 0.43 d−1 with HN, while cell concentrations peaked at 14,040 cells mL−1 (LN) and 11,000 cells mL−1 (HN) by the end of the exponential phase.
Overall, L. polyedra showed the highest specific growth and cell density in cultures at 25 °C, suggesting that this temperature favored the onset and duration of the exponential phase (Table 2, Figure 3).
Temperature showed a significant correlation with L. polyedra cell abundance (p = 0.00001), highlighting its strong influence on growth dynamics. In contrast, no statistically significant differences were detected between the low nutrient (LN) and high nutrient (HN) conditions. These findings suggest that L. polyedra concentrations are particularly sensitive to temperature, rather than nutrient availability (Supplementary Materials S1-A,B).

3.2. Effects of Temperature and Nutrients (NO3, PO4) on the Production of TEP, POC, PON, per Liter

3.2.1. Effect of Temperature and Nutrients (NO3, PO4) on TEP Production

TEP production varied significantly with temperature, ranging from 331 to 592 μg-XG L−1 (p = 0.00001). Nutrient availability also had a significant effect on TEP concentrations (p = 0.00963; Supplementary Material S1-C,D). The highest TEP level was recorded at 25 °C under low nutrient (LN) conditions (592 μg-XG L−1), while the lowest was observed at 17 °C with high nutrients (HN), reaching only 331 μg-XG L−1. At 20 °C, TEP levels were 492 μg-XG L−1 (LN) and 422 μg-XG L−1 (HN). The remaining treatments yielded intermediate values: 379 μg-XG L−1 at 17 °C (LN) and 362 μg-XG L−1 at 25 °C (HN) (Figure 4).

3.2.2. Effect of Temperature and Nutrients (NO3, PO4) on POC Production

The highest POC concentrations were recorded at 20 °C, with 476 mg L−1 under low nutrient (LN) conditions and 449 mg L−1 with high nutrients (HN). At 25 °C, the LN treatment yielded 434 mg L−1, while the lowest POC value among all treatments was observed under HN conditions at the same temperature. At 17 °C, POC concentrations remained relatively stable, with 429 mg L−1 (LN) and 396 mg L−1 (HN) (Table 3, Figure 4).
Overall, POC levels were relatively homogeneous across treatments, except for the reduced value at 25 °C with HN. Statistically significant differences in POC concentrations were found between temperatures (p = 0.00068), whereas the comparison between LN and HN nutrient treatments was not significant (Supplementary Material S1-E,F).

3.2.3. Effect of Temperature and Nutrients (NO3, PO4) on PON Production

PON concentrations were generally homogeneous across treatments, although some variation was evident with temperature and nutrient levels. At 17 °C, concentrations were 33 mg L−1 (LN) and 48 mg L−1 (HN). The highest PON values were observed at 20 °C, reaching 50 mg L−1 in the LN treatment and 60 mg L−1 with HN. At 25 °C, PON concentrations were 49 mg L−1 (LN) and 40 mg L−1 (HN) (Table 3, Figure 5).
Statistical analysis revealed significant differences in PON concentrations between temperatures (p = 0.01713), as well as between nutrient treatments (LN vs. HN; p = 0.01307) (Supplementary Material S1-G,H).

3.2.4. SIMPER, and PERMANOVA Analysis of the Temperature and Nutrient (NO3, PO4) Treatments

The SIMPER analysis showed that the effect of temperature on L. polyedra cultures was highly relevant (Supplementary Material S3-A). The factor that contributed to the differences in LN between the 17 and 20 °C cultures was the cell concentration (53%) and the concentration of TEP (25%). The factor that exhibited the greatest percentage difference between the 17 and 25 °C cultures was TEP, with a difference of 40%. Cell concentration exhibited the greatest difference between the 20 and 25 °C cultures, with a difference of 61%.
Conversely, the difference between cultures with HN was headed by TEP, with a 43% difference observed between 17 and 20 °C, while POC made the difference between 17 and 25 °C with a 39% difference. Furthermore, POC contributes 38% between the cultures at 20 and 25 °C. Finally, the difference between cultures at the same temperature with LN and HN was observed. At 17 °C, it was found that PON contributed 66%, while TEP contributed 15%. Similarly, the cultures established at 20 °C showed the PON with a contribution of 44%, while the cell concentration was observed to be in second place with a contribution of 32%. The products POC and TEP, with respective contributions of 40% and 35%, were the primary factors contributing to the observed differences within the cultures at 25 °C (Supplementary Material S3-A).
The two-way PERMANOVA analysis revealed that temperature had a highly significant effect on sample composition (pseudo-F = 89.25, p = 0.0001), explaining a substantial part of the observed variation. On the other hand, the nutrient factor had no significant effect (pseudo-F = 4.10, p = 0.0562), although the p value was close to the conventional threshold of significance (p = 0.05), suggesting a potentially marginal effect. Importantly, the interaction between temperature and nutrients was also significant (pseudo-F = 19.41, p = 0.0002) (Supplementary Material S1-I), indicating that the effect of temperature on composition depends on nutrient level, and vice versa.
This supports the need to analyze specific combinations of both factors to fully understand the variations in the samples evaluated and is consistent with the patterns observed in previous ANOVA analyses, where temperature showed a dominant effect on the measured variables, while differences by nutrients were less marked, but with relevant interactions. Consequently, the impact of temperature and nutrients on physiological processes in cultures and the subsequent production of exudates will be discussed in detail.

3.3. Comparison of TEP, POC, and PON Concentrations per Cell in L. polyedra Cultures

Since the concentrations of exudated TEP, POC, and PON normalized per cell did not meet the assumptions of normality and homoscedasticity required for ANOVA, a non-parametric Kruskal–Wallis test was applied, followed by Dunn’s post hoc test with Bonferroni correction to assess significant differences among experimental treatments.

3.3.1. Concentrations of TEP per Cell

The lowest TEP values per cell were recorded at 17 °C, with 0.04 μg-XG cell−1 in the LN treatment and 0.01 μg-XG cell−1 in the HN treatment. In contrast, the highest values occurred at 20 °C: 0.06 μg-XG cell−1 (LN) and 0.05 μg-XG cell−1 (HN). At 25 °C, intermediate values of 0.05 μg-XG cell−1 (LN) and 0.03 μg-XG cell−1 (HN) were observed (Table 4, Figure 6).
Significant differences were detected only between the following treatment pairs: 20-LN vs. 25-HN and 20-HN vs. 25-HN (p = 0.006063). However, no statistically significant differences were found between LN and HN treatments within each temperature condition (Supplementary Material S2-A,B).

3.3.2. Comparison of POC Concentrations per Cell

At 17 °C, POC concentrations per cell were relatively uniform, with values of 0.046 mg cell−1 (LN) and 0.044 mg cell−1 (HN). The highest per-cell POC concentrations were recorded at 20 °C, reaching 0.068 mg cell−1 with LN and 0.059 mg cell−1 with HN. In contrast, POC concentrations decreased at 25 °C, with values of 0.035 mg cell−1 (LN) and 0.022 mg cell−1 (HN) (Table 4, Figure 6).
Statistical analysis revealed significant differences in POC per cell between the 20-LN and 25-LN cultures, as well as between 20-LN and 25-HN (p = 0.0008836). In addition, nutrient availability had a significant effect on POC concentration per cell across treatments (p = 0.00963) (Supplementary Material S2-C,D).

3.3.3. Comparison of PON Concentrations per Cell

The highest PON concentrations per cell were recorded at 20 °C, with values of 0.0094 mg cell−1 under LN conditions and 0.0083 mg cell−1 with HN. At 17 °C, L. polyedra cultures showed lower concentrations of 0.0036 mg cell−1 (LN) and 0.0056 mg cell−1 (HN), which were comparable to those observed at 25 °C: 0.0040 mg cell−1 (LN) and 0.0036 mg cell−1 (HN) (Table 4, Figure 6).
However, statistical analysis revealed no significant differences in PON concentration per cell across temperature or nutrient treatments (Supplementary Material S2-E,F).

3.3.4. SIMPER, and PERMANOVA Analysis of Temperature and Nutrient (NO3, PO4) Treatments in per Cell Calculations

SIMPER comparative analyses between temperatures under low nutrient (LN) conditions revealed that POC was the primary variable distinguishing the cultures. In the comparison between 17 °C and 20 °C, POC accounted for 75% of the observed differences. Similarly, between 17 °C and 25 °C, POC contributed 55%, followed by TEP with 42%. The comparison between 20 °C and 25 °C also highlighted POC as the main discriminating factor (68%), with TEP contributing 20%.
Under high nutrient (HN) conditions, TEP was the dominant variable differentiating cultures. Between 17 °C and 20 °C, TEP contributed 75% to the observed differences. In the 17 vs. 25 °C comparison, TEP accounted for 49% and POC for 46%. For the 20 vs. 25 °C comparison, POC was responsible for 51% of the difference, followed by TEP at 41%.
Intra-temperature comparisons between nutrient treatments also emphasized the role of TEP. At 17 °C, TEP explained 88% of the difference between LN and HN cultures. At 20 °C, TEP accounted for 68%, and at 25 °C, TEP and POC per cell contributed 55% and 43%, respectively. Overall, TEP emerged as the main factor explaining the variation between nutrient treatments (LN vs. HN), regardless of temperature (Supplementary Material S3-B).
The result of the two-way PERMANOVA showed that temperature exerted a highly significant effect on the multivariate structure of the samples (pseudo-F = 27.25, p = 0.0001), indicating that thermal changes strongly modulate the per-cell characteristics of PET, POC, and PON. Furthermore, the nutrient factor was also significant after normalization (pseudo-F = 6.68, p = 0.0116), suggesting that nutrient availability influences the distribution of these fractions when controlling cell abundance. Finally, the temperature nutrients interaction was not significant (pseudo-F = 1.998, p = 0.1502, see Supplementary Material S2-G), evidence that, once adjusted for cellular data, both factors operate additively and without detectable synergistic effects. These findings highlight the importance of using normalized metrics to reveal independent influences of environmental factors on particulate matter production in L. polyedra cultures.

3.4. POC:PON Ratio

The POC:PON ratio varied with temperature and nutrient availability. Under low nutrient (LN) conditions, the highest ratios were observed, reaching values of 12.4 at 17 °C, 10.8 at 20 °C, and 8.6 at 25 °C. In contrast, under high nutrient (HN) conditions, the ratios were consistently lower: 7.9 at 17 °C, 7.3 at 20 °C, and 6.1 at 25 °C (Figure 7).

4. Discussion

4.1. Effects of Temperature and Nutrients on the Cultures of L. polyedra

The highest growth rate of L. polyedra was detected at 25 °C in both nutrient concentrations. Although the strain was isolated from Todos Santos Bay (Mexican Pacific), where surface temperatures generally range between 17 and 21 °C [27], its optimal growth in this study was observed at 25 °C—a value that exceeds the typical environmental conditions of its native habitat. This elevated temperature was thus considered a high or stressful condition, simulating future ocean warming scenarios. Ecologically, such temperatures may become more frequent under climate change and could favor the proliferation of bloom-forming dinoflagellates such as L. polyedra [22,23], this, in turn, may promote greater exudation of carbon-rich compounds and facilitate the formation of organic aggregates in coastal environments.
Previous studies on phytoplankton species have reported optimal growth within a temperature range of 18–28 °C [22], with L. polyedra proliferation observed at surface temperatures as low as 17 °C along the Iberian Peninsula [39]. In laboratory conditions, the optimal growth temperature for L. polyedra has generally been reported around 19 ± 1 °C [40,41]. However, the present study demonstrated that cultures of L. polyedra exhibited enhanced growth at 25 °C compared to 17 °C and even 20 °C, suggesting that elevated temperatures may favor the development of this species. These findings align with previous reports identifying temperature as a key environmental driver of phytoplankton growth [42].
This trend was observed in both experiments, regardless of the nutrient concentration. However, the behavior of the culture at 20 °C was variable, exhibiting a lower growth rate and a less defined exponential phase. So, the addition of nitrate and phosphate to the culture medium does not enhance the growth of L. polyedra.
However, in cultures of L. polyedra with temperatures of 24 °C, Figueroa and Bravo [43] demonstrated that the increase or decrease of nutrients (NO3 and PO4), particularly phosphate, plays an important role in the type of cyst formed (resting cyst or temporary cyst) and total cyst production. This, in turn, determines the ecological and sexual role of cyst formation by L. polyedra. Furthermore, they reported that the formation of asexual and sexual cysts of L. polyedra, including a haploid ecdysal asexual cyst, another sexual ecdysal type diploid cyst, and a diploid spiny resting cyst, is temperature dependent [43]. In the cultures observed in the present investigation, it was possible to observe during the exponential phase of the cultures subject to 25 °C, the generation of different temporary cysts together with vegetative cells of smaller size. In contrast, the cultures at 17 °C and 20 °C exhibited a life cycle maintained mostly by cells in the vegetative state with superior size.
These results support the idea that increased temperature can stimulate rapid growth of certain phytoplankton species, provided there is adequate solar radiation and nutrient supply [22,33,44,45]. Previous studies have demonstrated a correlation between elevated summer temperatures and the occurrence of phytoplankton blooms in Todos Santos Bay [32]. Consequently, the projected increase in global temperatures may facilitate the proliferation of harmful algal blooms across the globe.
The patterns observed in specific growth rates (μ) reinforce the dominant role of temperature in modulating the physiology of L. polyedra. The highest μ values were recorded at 25 °C, both under low (0.45 d−1) and high (0.43 d−1) nutrient conditions. At 17 °C, intermediate rates were observed (0.42 d−1 for LN and 0.41 d−1 for HN), while the lowest growth rates occurred at 20 °C (0.37 d−1 for LN and 0.38 d−1 for HN). Interestingly, this temperature also corresponded to lower levels of exudate production (TEP and POC), suggesting a coupled decline in both growth and extracellular carbon release. In contrast, cultures at 25 °C not only grew more rapidly but also exhibited elevated TEP and, to a lesser extent, POC concentrations, particularly under low nutrient supply. This parallel behavior suggests that higher temperatures stimulate both cellular proliferation and exudate production, while suboptimal thermal conditions such as 20 °C may impair both processes, potentially due to physiological stress or altered microbial interactions.

4.2. Effect of Temperature and Nutrients (NO3, PO4) on TEP Production

The present study demonstrates that temperature and to a lesser degree nutrients (nitrate and phosphate) are key factors affecting the production of TEP in L. polyedra. TEP production per liter was significantly influenced by temperature. A production range between 331 to 592 μg-XG L−1. The highest TEP concentration was observed at 25 °C with LN concentrations and the lowest concentration was recorded at 17 °C with HN. These results are consistent with the findings of other phytoplankton species, which indicate that the increase in temperature promotes the production of TEP [22,46]. Temperature had a significant effect on cell growth and exudate production in L. polyedra cultures. At 25 °C, cells reached the highest density and highest concentration of TEP, particularly under conditions of low nutrient supply. In contrast, at 20 °C, the lowest growth rate was recorded, with lower production of POC and TEP. Although nutrients did not show a statistically significant effect on their own in all cases, they did interact significantly with temperature. In general, the low nutrient supply (LN) regime promoted higher TEP production, suggesting a compensatory mechanism in which cells under nutritional stress redirect carbon toward extracellular exudation [17,24].
The interaction between temperature and cell growth may explain the observed variation in TEP production. At high temperatures (25 °C), accelerated cell growth is likely to result in higher production of TEP due to increased metabolic and photosynthetic activity [2]. At lower temperatures (17 °C), slower cell growth may limit the production of TEP, even with higher nutrient availability.
The increased availability of nutrients could allow L. polyedra cells to produce more TEP to support cellular functions and metabolic processes at the early onset of proliferation and remain until the stationary-death phase, as observed in the present study cultures at 17 and 20 °C. The highest values of TEP per cell were observed at LN concentrations. At HN concentrations, TEP production decreased except for the temperature at 20 °C. These results indicate that the availability of nitrate (NO3) and phosphate (PO4) is a determining factor in producing TEP in L. polyedra. This indicates that nutrient availability is a limiting factor for TEP synthesis, but that excess may also represent a limiting.
Although there is no similar study with L. polyedra to compare the results found here, has been reported a strain measurement CCMP 406 (Gonyaulax polyedra) which generated 329 μg-XG L−1 can be found in Passow [47]. In addition, it has been that the TEP per cell is related to cell concentration, species-specific surface area, and physiology in other species [18]. Nutrients provide the fundamental elements required for the synthesis of organic compounds, including TEP and different production rates have been reported among strains of the same species. The intra-species variability in the production of TEP is influenced by differences in culture conditions, including factors such as temperature and nutrients. Irradiance also plays a notable role in these changes, with the mechanisms of photoacclimation varying interspecifically for both light harvesting and subsequent photosynthetic metabolism [24,48].
Temperature and nutrients may act synergically to optimize photosynthetic efficiency and TEP production in L. polyedra. We documented the highest production of TEP at 25 °C with LN, while the lowest concentration was observed at 17 °C with HN. This suggests that at high temperatures, the availability of adequate nutrients could maximize the ability of cells to produce TEP. Conversely, at low temperatures, even high nutrient availability may not be sufficient to achieve maximal levels of TEP production. The duality between photosynthetic activity and TEP production has already been described, which provides a new focus on carbon excretion, attributed mainly to nutritional stress [24,49].
These results confirm that temperature is the primary modulating factor in the production of TEP by L. polyedra, exerting a significant influence both on total concentrations and on values normalized per cell. Nevertheless, a significant interaction between temperature and nutrient availability was detected, particularly evident in the PERMANOVA analysis. This interaction suggests that the effect of temperature on TEP exudation is modulated by the nutrient regime. Specifically, the combination of high temperature (25 °C) and low nutrient availability (LN) led to the highest TEP concentrations, supporting the hypothesis that, under nutrient-limited conditions, excess photosynthetically fixed carbon is diverted toward extracellular release. This compensatory mechanism likely operates when cellular growth is constrained by nitrogen or phosphorus availability, resulting in increased exudation of polysaccharides into the environment [22,24,50,51].
In the event of nitrogen limitation, phytoplankton may prioritize carbon fixation while accumulating excess carbon as TEP. Production serves a variety of functions, including carbon exudation, cell aggregation, and defense mechanisms. Additionally, it is essential for the synthesis of amino acids, nucleic acids, chlorophylls, and toxins. In the context of nitrogen stress, dinoflagellates make metabolic and trophic strategy modifications to ensure survival [52].
The present study demonstrates that the TEP exudation increased at high temperatures while the availability of nutrients, particularly nitrate and phosphate, could have a positive effect on photosynthetic efficiency. The latter is relevant to PET formation represents an important pathway by which dissolved organic matter (DOM) is converted to POC [2].
The observed increase in TEP production under conditions of high temperature and nutrient limitation may have important ecological and environmental implications. TEP facilitates the aggregation of cells and particles, enhancing floc formation and vertical export through the biological carbon pump. This process can lead to a partial decoupling of surface carbon and nitrogen cycles [22,46,53]. Moreover, the accumulation of TEP can promote the proliferation of opportunistic heterotrophic bacteria, alter microbial community metabolism, and influence the dynamics and persistence of harmful algal blooms (HABs) [46,54,55]. These effects may intensify hypoxia in subsurface layers and restructure local food webs.
From an applied perspective, elevated concentrations of TEP are frequently associated with bloom events and increased organic loading in coastal waters. This accumulation contributes to biofouling in filtration systems and has been identified as a critical operational challenge for seawater desalination plants, often requiring shutdowns for cleaning and maintenance [56,57,58]. Therefore, understanding the environmental drivers of TEP formation, such as temperature and nutrient availability, is essential not only for predicting carbon export dynamics but also for managing water quality in impacted coastal regions.

4.3. Effect of Temperature and Nutrients (NO3, PO4) on POC Production

High POC concentration was observed as the temperature increased, reaching a maximum of 476 mg L−1 at 20 °C and 434 mg L−1 at 25 °C with LN. Consequently, the availability of nutrients, particularly nitrate and phosphate, also exert a significant influence on the production of POC. Since decoupling between carbon fixation and growth rate caused by nutrient depletion, can have an impact on the exudation of organic compounds to free cells from excess carbon generated during photosynthesis [48,59]. This would probably explain the maximum POC values observed at 20 °C, as well as in the case of 25 °C at the stationary growth phase of this study. It has already been reported that nutrients are limiting in this phase and the exudation of organic compounds increases. Moreover, in the case of dinoflagellates, a higher rate of respiration-photosynthesis has been recorded compared to other phytoplankton groups during exponential growth phase, fixing more than 40% of the carbon photosynthetically during the stationary phase [60]. These high respiration rates are attributed to the large content of genetic material and the energetic cost of cell replication.
In contrast, the combination of high temperature (25 °C) and HN concentration yielded the lowest POC value. This phenomenon may be attributed to the inhibitory effect of excess nutrients on microbial activity, which in turn impedes the decomposition of organic matter and the production of POC [7]. This interpretation is consistent with preliminary analyses of the bacterial community associated with L. polyedra, which revealed notable shifts in composition across temperature treatments. At 20 °C (where reduced cell growth and intermediate exudate production were observed), the bacterial assemblage was dominated by Rhodobacteraceae (in LN condition) and Hyphomonadaceae (Hyphomonas, in HN condition), groups known for their active roles in nutrient cycling, vitamin B12 production, and signaling processes that can modulate algal physiology [61,62,63,64,65,66,67]. In contrast, cultures at 17 °C were enriched in Flavobacteriaceae, which are associated with organic matter transformation and mutualistic interactions that may have favored dinoflagellate growth [61,68]. At 25 °C, we observed a predominance of Polaribacter and Colwellia, taxa capable of degrading organic polymers and adapting to variable environmental conditions [69,70,71]. Although our data do not allow us to establish a direct causal relationship, the predominant presence of these families at 20 °C suggests a possible scenario in which bacteria-dinoflagellate interactions may have negatively affected the proliferation of L. polyedra. This effect could result from competition for limited resources (e.g., vitamins or reduced nitrogen), the alteration of chemical signals in the phycosphere, or the production of inhibitory compounds [72,73,74]. These findings suggest that the observed physiological differences among cultures may be influenced not only by temperature and nutrients but also by microbial interactions within the phycosphere. However, further genomic and functional analyses are needed to establish these relationships more robustly. This aspect is of utmost importance and will be addressed in a separate study.
Nutrient availability also exerted a significant impact on POC concentrations. In general, higher POC concentrations were observed with LN concentration compared to HN. This could be due to an inhibitory effect of excess nutrients on biological activity, limiting organic carbon production. Additionally, increased temperature promoted TEP production, which could be attributed to higher growth rates and increased carbon fixation by continuous photosynthesis. To maintain a balanced intracellular carbon content at high temperatures (POC content changed at 20 °C and 25 °C), it is possible that excess carbon was released to the environment from phytoplankton cells, increasing peripheral TEP concentration [22].
On the role of nitrate, it has been reported that adding it to pre-acclimated cultures to nitrogen deficiency has the effect of increasing their resistance to deficiency. In this study, L. polyedra cultures showed remarkable resistance, maintaining viability for almost two months at high cell densities. In contrast, it has been reported that cells that had not undergone prior acclimation exhibited a decrease in viability after two weeks [75]. Following severe nitrogen deficiency, dinoflagellates exhibit a survival strategy involving the activation of mechanisms to prolong their viability. This strategy is based on cell cycle arrest and reduced photosynthetic activity, which together minimize nitrogen consumption and redirect energy towards cell maintenance processes. The inability to synthesize new amino acids in the context of active photosynthesis leads to the accumulation of reduced carbon in the form of starch granules and lipid bodies, which provide access to different energy sources or contribute to the regulation of cell processes under stress conditions [76], this process may have been active in cultures at 25 °C with both nutrient treatments.

4.4. POC:PON Ratio

The ratio of particulate organic carbon to particulate organic nitrogen (POC:PON) is a recognized index for assessing the nutritional status and physiological behavior of phytoplankton [77]. The POC:PON ratio in L. polyedra in the stationary phase of growth was 12.4 the highest, and 8.6 the lowest in LN. In HN the highest value was 7.9, and 6.1 was the lowest. Mesocosm experiments have demonstrated that, under conditions where nutrients restrict biomass growth but do not impede photosynthesis, algae offload their excess fixed carbon as polysaccharide exudates, which then aggregate into TEP. After TEP is formed, the particulate organic carbon:nitrogen ratio steadily climbs in the post-proliferation phase. In this way, TEP production severs the usual coupling of carbon and nitrogen cycling, channeling a large portion of the newly fixed carbon—up to 44 % of total primary production—into the TEP pool [78].
A comparable POC:PON ratio was documented in the stationary phase in Prorocentrum minimum [79,80]. Similarly, nitrogen limitation in dinoflagellates have demonstrated alterations in the POC:PON ratio, with values comparable to those observed here (9.53) in Alexandrium fundyense [81]. Likewise, Prorocentrum shikokuense presented a POC:PON ratio at 25 °C of 6.68, like that reported in this study of 6.1 for L. polyedra. It should be noted that the species P. shikokuense was maintained over a range of temperatures (19–28 °C), showing a decrease in the POC:PON ratio as temperature increased [82]. This inverse relationship between POC:PON ratio and temperature was also present in the present experiment.
Finally, proteomics was employed to determine the expression of proteins related to photoreaction and light uptake, which was found to be maximized at 28 °C while the cells were under heat stress. At 28 °C, the abundance of photosynthetic antenna proteins was found to be significantly elevated in comparison to 25 °C. Furthermore, carbon metabolism was enhanced and a higher production of secondary metabolite biosynthesis, and amino acid biosynthesis was detected [82].

5. Conclusions

This study demonstrates that temperature is a key driver in the physiology of L. polyedra, significantly modulating both cell growth and the production of organic exudates, particularly transparent exopolymeric particles (TEP). At 25 °C—a temperature above the average environmental range in the strain’s isolation site (Bahía de Todos Santos, 17–21 °C)—the highest specific growth rates were recorded, reaching up to 0.45 d−1 under low nutrient (LN) conditions. This treatment also yielded the highest TEP concentrations (592 μg-XG L−1), indicating that high temperature combined with nutritional stress promotes the exudation of excess photosynthetic carbon when growth is limited by nitrogen or phosphorus.
In contrast, at 20 °C, cultures exhibited atypically low growth rates (0.37–0.38 d−1) and reduced exudate production. This deviation may be explained by physiological constraints or by microbial interactions, as suggested by preliminary analyses of the bacterial communities associated with the cultures. Distinct bacterial assemblages were detected at each temperature. These shifts may influence nutrient recycling, vitamin production, and host–microbe signaling, ultimately modulating dinoflagellate performance and exudation.
A strong parallel was observed between growth efficiency and exudate release, indicating a coupled physiological response to temperature. Moreover, the increased TEP production under warming and nutrient stress reflects a decoupling of the carbon and nitrogen cycles, with a greater fraction of fixed carbon channeled into the extracellular pool. Ecologically, such responses may enhance particle aggregation, favor vertical flux via the biological pump, stimulate heterotrophic bacterial activity, and intensify hypoxia in subsurface waters—especially during dense blooms of L. polyedra.
At an applied level, the accumulation of TEP poses a risk to the operational efficiency of seawater desalination plants, as these sticky exopolymers contribute to membrane fouling and clogging. Given projected increases in ocean surface temperatures due to climate change, TEP formation in bloom-forming dinoflagellates is expected to become more frequent and intense.
This work contributes to a deeper understanding of how abiotic factors such as temperature and nutrient availability regulate exudate dynamics in dinoflagellates, with implications for biogeochemical cycling, bloom ecology, and coastal management. Future studies in natural systems are essential to validate these findings under more complex ecological conditions.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/phycology5030042/s1, Supplementary Material S1, S2, and S3.

Author Contributions

Conceptualization, R.C.-Q. and G.S.-R.; formal analysis, M.C.R.-d.l.T., G.S.-R. and R.C.-Q.; investigation and methodology, R.C.-Q. and M.M.-H.; writing—original draft preparation, R.C.-Q. and M.C.R.-d.l.T.; writing—review and editing, G.S.-R., M.C.R.-d.l.T. and E.G.-M.; resources, E.G.-M. and M.C.R.-d.l.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research was carried out during the postdoctoral fellowship (CVU 617226) at the Secretariat for Science, Humanities, Technology, and Innovation (SECIHTI) in the Faculty of Marine Sciences, Autonomous University of Baja California. It forms part of the project “Addressing the Challenges Associated with Harmful Algal Blooms in Baja California: Integrating Knowledge to Meet Socio-Environmental and Economic Needs”, funded by the SECIHTI-PRONAII Sectorial Fund under project PRONACES 319104.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Acknowledgments

We sincerely thank Helmut Maske Rubach and César Alameda Jáuregui from the Marine Microbial Ecology Laboratory (MICMAR) of the Biological Oceanography Department at CICESE for their valuable assistance and collaboration in the measurement and processing of particulate organic carbon (POC) and particulate organic nitrogen (PON). Their support was essential for the development of this work.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
LNLow nutrient
HNHigh nutrient
TEPTransparent Exopolymer Particles
POCParticulate Organic Carbon
PONParticulate Organic Nitrogen
ANOVAAnalysis of Variance
PERMANOVAPermutational Multivariate Analysis of Variance
SIMPERSimilarity Percentage
HABsHarmful Algal Blooms

Appendix A

Table A1. F2 Medium Composition (for 1 L).
Table A1. F2 Medium Composition (for 1 L).
ComponentQuantity UsedNotes/Stock Solution
Main F2 Medium components
NaNO31 mLStock solution: 75 g · L−1 dH2O
NaH2PO4 · H2O1 mLStock solution: 5 g · L−1 dH2O
Na2SiO3 · 9H2O1 mLStock solution: 30 g · L−1 dH2O
Trace Metals Solution1 mLSee detailed components below
Vitamins Solution0.5 mLSee detailed components below
Trace metals solution components Dissolve in 950 mL dH2O, bring to 1 L.
FeCl3 · 6H2O3.15 g
Na2EDTA · 2H2O4.36 g
MnCl2 · 4H2O1 mLStock solution: 180.0 g · L−1 dH2O
ZnSO4 · 7H2O1 mLStock solution: 22.0 g · L−1 dH2O
CoCl2 · 6H2O1 mLStock solution: 10.0 g · L−1 dH2O
CuSO4 · 5H2O1 mLStock solution: 9.8 g · L−1 dH2O
Na2MoO4 · 2H2O1 mLStock solution: 6.3 g · L−1 dH2O
Vitamins solution components Dissolve in 950 mL dH2O, add 1 mL of primary stocks, bring to 1 L. Filter-sterilize and store frozen.
Thiamine · HCl (vitamin B1)200 mg
Biotin (vitamin H)1 mLStock solution: 1.0 g · L−1 dH2O
Cyanocobalamin (vitamin B12)1 mLStock solution: 1.0 g · L−1 dH2O
Note: For the HN medium, the quantity of NaNO3 and NaH2PO4 · H2O stock solutions used is doubled. All other components remain the same unless otherwise specified for a different fortification.

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Phycology 05 00042 g001
Figure 1. Linguloaulax polyedra observed under a light microscope (60× objective). and collected in Todos Santos Bay. Scale bar = 20 µm.
Figure 1. Linguloaulax polyedra observed under a light microscope (60× objective). and collected in Todos Santos Bay. Scale bar = 20 µm.
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Figure 2. Growth of L. polyedra cultivated at 17, 20, and 25 °C under a low nutrient concentration regime (LN: NO3 at 0.075 gL−1 of NO3 and 0.005 gL−1 of PO4).
Figure 2. Growth of L. polyedra cultivated at 17, 20, and 25 °C under a low nutrient concentration regime (LN: NO3 at 0.075 gL−1 of NO3 and 0.005 gL−1 of PO4).
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Figure 3. Growth of L. polyedra cultivated at 17, 20, and 25 °C under a high nutrient concentration regime (HN:NO3 at 0.15 gL−1 and PO4 at 0.01 gL−1).
Figure 3. Growth of L. polyedra cultivated at 17, 20, and 25 °C under a high nutrient concentration regime (HN:NO3 at 0.15 gL−1 and PO4 at 0.01 gL−1).
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Figure 4. Concentration of TEP (μg-XG L−1), POC (mg L−1), and cell concentration (cell mL−1). Three culture temperatures at 17 °C, 20 °C and 25 °C with LN, and HN.
Figure 4. Concentration of TEP (μg-XG L−1), POC (mg L−1), and cell concentration (cell mL−1). Three culture temperatures at 17 °C, 20 °C and 25 °C with LN, and HN.
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Figure 5. PON concentration (mg L−1) and cell concentration (cell mL−1) quantified in L. polyedra culture, three culture temperatures at 17 °C, 20 °C, and 25 °C with LN, and HN.
Figure 5. PON concentration (mg L−1) and cell concentration (cell mL−1) quantified in L. polyedra culture, three culture temperatures at 17 °C, 20 °C, and 25 °C with LN, and HN.
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Figure 6. A comparison of the concentration per cell of TEP (μg-XG cell), POC (mg cell), and PON (mg cell) on L. polyedra culture. Culture temperatures were employed: 17 °C, 20 °C, and 25 °C, with an LN and HN concentration.
Figure 6. A comparison of the concentration per cell of TEP (μg-XG cell), POC (mg cell), and PON (mg cell) on L. polyedra culture. Culture temperatures were employed: 17 °C, 20 °C, and 25 °C, with an LN and HN concentration.
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Figure 7. Ratio POC/PON (mol/mol−1), quantified in L. polyedra culture. Culture temperatures at 17 °C, 20 °C, and 25 °C with the LN concentration and HN.
Figure 7. Ratio POC/PON (mol/mol−1), quantified in L. polyedra culture. Culture temperatures at 17 °C, 20 °C, and 25 °C with the LN concentration and HN.
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Table 1. Nitrate (NO3) and phosphate (PO4) concentrations in L. polyedra cultures at 17, 20, and 25 °C under low (LN) and high (HN) nutrient regimes.
Table 1. Nitrate (NO3) and phosphate (PO4) concentrations in L. polyedra cultures at 17, 20, and 25 °C under low (LN) and high (HN) nutrient regimes.
T °CNO3 gL−1PO4 gL−1
17-LN0.0750.005
17-HN0.150.01
20-LN0.0750.005
20-HN0.150.01
25-LN0.0750.005
25-HN0.150.01
Table 2. Specific growth rate (div d−1) of L. polyedra cultivated at 17, 20, and 25 °C under low (LN) and high (HN) nutrient regimes. The growth rate was calculated during the exponential growth phase of the culture.
Table 2. Specific growth rate (div d−1) of L. polyedra cultivated at 17, 20, and 25 °C under low (LN) and high (HN) nutrient regimes. The growth rate was calculated during the exponential growth phase of the culture.
LNHN
25 °C0.45 d−10.43 d−1
20 °C0.37 d−10.38 d−1
17 °C0.42 d−10.41 d−1
Table 3. Concentration of TEP (μg-XG L−1), POC (mg L−1), PON (mg L−1), and cell concentration (cell mL−1) quantified in L. polyedra culture, three culture temperatures at 17 °C, 20 °C, and 25 °C with LN, HN.
Table 3. Concentration of TEP (μg-XG L−1), POC (mg L−1), PON (mg L−1), and cell concentration (cell mL−1) quantified in L. polyedra culture, three culture temperatures at 17 °C, 20 °C, and 25 °C with LN, HN.
μg-XG L−1mg POC L−1mg PON L−1Cell mL−1
17 °C LN379 ± 4.87429 ± 75.8233 ± 4.199283 ± 556
17 °C HN331 ± 14.51396 ± 32.6948 ± 3.418670 ± 306
20 °C LN492 ± 12.37476 ± 36.6150 ± 4.767920 ± 486
20 °C HN422 ± 1.66449 ± 3.9360 ± 3.187766 ± 143
25 °C LN592 ± 11.83434 ± 6.1449 ± 0.3914,040 ± 85
25 °C HN362 ± 4.55248 ± 11.4640 ± 1.4411,000 ± 158
Table 4. Concentration per cell of TEP (μg-XG cell−1), POC (mg cell−1), and PON (mg cell−1) on L. polyedra culture. Culture temperatures at 17 °C, 20 °C, and 25 °C with LN concentration and HN.
Table 4. Concentration per cell of TEP (μg-XG cell−1), POC (mg cell−1), and PON (mg cell−1) on L. polyedra culture. Culture temperatures at 17 °C, 20 °C, and 25 °C with LN concentration and HN.
μg-XG Cellmg POC Cellmg PON Cell
17 °C LN0.041 ± 0.0020.046 ± 0.0050.0036 ± 0.0003
17 °C HN0.010 ± 0.0050.044 ± 0.0010.0056 ± 0.0001
20 °C LN0.040 ± 0.0020.068 ± 0.0030.0094 ± 0.0004
20 °C HN0.062 ± 0.0010.059 ± 0.0010.0083 ± 0.0004
25 °C LN0.050 ± 0.0020.035 ± 0.0010.0040 ± 0.0001
25 °C HN0.033 ± 0.0000.022 ± 0.0010.0036 ± 0.0001
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Castañeda-Quezada, R.; Ruiz-de la Torre, M.C.; Samperio-Ramos, G.; García-Mendoza, E.; Matus-Hernández, M. Temperature and Nutrient Effects on Organic Exudate Production in Lingulaulax polyedra (Stein) Head et al., 2024 Cultures. Phycology 2025, 5, 42. https://doi.org/10.3390/phycology5030042

AMA Style

Castañeda-Quezada R, Ruiz-de la Torre MC, Samperio-Ramos G, García-Mendoza E, Matus-Hernández M. Temperature and Nutrient Effects on Organic Exudate Production in Lingulaulax polyedra (Stein) Head et al., 2024 Cultures. Phycology. 2025; 5(3):42. https://doi.org/10.3390/phycology5030042

Chicago/Turabian Style

Castañeda-Quezada, Rigel, Mary Carmen Ruiz-de la Torre, Guillermo Samperio-Ramos, Ernesto García-Mendoza, and Miguel Matus-Hernández. 2025. "Temperature and Nutrient Effects on Organic Exudate Production in Lingulaulax polyedra (Stein) Head et al., 2024 Cultures" Phycology 5, no. 3: 42. https://doi.org/10.3390/phycology5030042

APA Style

Castañeda-Quezada, R., Ruiz-de la Torre, M. C., Samperio-Ramos, G., García-Mendoza, E., & Matus-Hernández, M. (2025). Temperature and Nutrient Effects on Organic Exudate Production in Lingulaulax polyedra (Stein) Head et al., 2024 Cultures. Phycology, 5(3), 42. https://doi.org/10.3390/phycology5030042

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