Oceans

Research

14 pages, 4258 KiB

Open AccessArticle

Widespread Coral Bleaching and Mass Mortality of Reef-Building Corals in Southern Mexican Pacific Reefs Due to 2023 El Niño Warming

by Andrés López-Pérez, Rebeca Granja-Fernández, Eduardo Ramírez-Chávez, Omar Valencia-Méndez, Fabián A. Rodríguez-Zaragoza, Tania González-Mendoza and Armando Martínez-Castro

Oceans 2024, 5(2), 196-209; https://doi.org/10.3390/oceans5020012 - 4 Apr 2024

Cited by 2 | Viewed by 4699

Abstract

In May 2023, oceanic and atmospheric anomalies indicated El Niño conditions in the eastern Pacific, followed by coral bleaching in coral communities and reefs of Huatulco. We conducted surveys and sampled coral reef communities from late June to mid–August of 2023 to evaluate [...] Read more.

In May 2023, oceanic and atmospheric anomalies indicated El Niño conditions in the eastern Pacific, followed by coral bleaching in coral communities and reefs of Huatulco. We conducted surveys and sampled coral reef communities from late June to mid–August of 2023 to evaluate the intensity and extent of the changes associated with the warming event. From January of 2023, Huatulco experienced positive sea surface temperature (SST) anomalies; however, beginning in June, the high-temperature anomalies became extreme (>31 °C; ~2 °C above historical records). These high temperatures resulted in extensive coral bleaching in middle–late June and mortality from middle–late July (>50–93%). In addition, the area experienced significant reductions in echinoderm abundance and fish biomass. In 2023, severe bleaching affected coral systems in the Central Mexican Pacific, Gulf of Mexico, and Mexican Caribbean, making this the most devastating marine heatwave event, simultaneously impacting coral reefs across Mexico’s Pacific and Atlantic coasts. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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16 pages, 3779 KiB

Open AccessArticle

Effects of Food Concentration and Light Intensity on the Growth of a Model Coral

by Tung-Yung Fan, Yan-Leng Huang and Anderson Mayfield

Oceans 2024, 5(2), 150-165; https://doi.org/10.3390/oceans5020009 - 25 Mar 2024

Cited by 1 | Viewed by 1508

Abstract

Since reef-building corals rely on both heterotrophy and endosymbiotic dinoflagellate autotrophy to meet their metabolic needs, it is necessary to consider both food supply and light levels, respectively, when optimizing their cultivation ex situ. Herein nubbins of the model reef coral Pocillopora [...] Read more.

Since reef-building corals rely on both heterotrophy and endosymbiotic dinoflagellate autotrophy to meet their metabolic needs, it is necessary to consider both food supply and light levels, respectively, when optimizing their cultivation ex situ. Herein nubbins of the model reef coral Pocillopora acuta cultured in recirculating aquaculture systems at photosynthetically active radiation levels of 370 or 670 μmol quanta m⁻² s⁻¹ were fed Artemia nauplii at concentrations of either 33 or 78 individuals mL⁻¹ in a separate feeding tank for 6 hr in the dark thrice weekly. A subset of nubbins was experimentally wounded at the outset of the 84-day experiment to assess recovery, and 100% fully healed within 2–4 weeks. All cultured corals survived, and unwounded corals (1) grew at a specific growth rate approaching 0.5% day⁻¹ and (2) demonstrated a mean total linear extension of 0.2% day⁻¹ (~6–8 cm year⁻¹); these are far higher than growth rates normally documented in situ. In the feeding tank, corals tolerated nitrate levels up to 25 mg L⁻¹, but once concentrations reached 50 mg L⁻¹ by day 84, tissue necrosis began to occur in nubbins of one tank. This highlights the importance of feeding in separate tanks during long-term culture of corals, and bio-filtration could reduce the possibility of organic matter accumulation in future coral culture studies. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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17 pages, 1764 KiB

Open AccessArticle

Herbivorous Reef Fish Interaction with the Habitat and Physicochemical Variables in Coral Ecosystems in the Mexican Tropical Pacific

by Diana Morales-de-Anda, Amílcar Leví Cupul-Magaña, Consuelo María Aguilar-Betancourt, Gaspar González-Sansón, Fabián Alejandro Rodríguez-Zaragoza and Alma Paola Rodríguez-Troncoso

Oceans 2024, 5(1), 21-37; https://doi.org/10.3390/oceans5010002 - 4 Jan 2024

Viewed by 1850

Abstract

Herbivorous fish can mediate spatial competition between algae and corals, which is crucial for coral ecosystems. However, in areas with limited coral coverage like the Mexican tropical Pacific (MTP), this dynamic is not fully understood. This study, using a functional trait approach and [...] Read more.

Herbivorous fish can mediate spatial competition between algae and corals, which is crucial for coral ecosystems. However, in areas with limited coral coverage like the Mexican tropical Pacific (MTP), this dynamic is not fully understood. This study, using a functional trait approach and ordination analysis, explores whether herbivorous reef fish assemblage influences the benthic habitat components or if physicochemical factors define the habitat variability in the MTP’s Cleofas and Marietas insular systems. We analyzed if this relationship persisted across systems and over time, and identified species traits tied to habitat variability. Island comparison analyses between Cleofas and Marietas reveal that both herbivorous reef fish and physicochemical variables shape the habitat. Cleofas had larger mobile herbivorous fish that formed groups related mostly to macroalgae cover. In contrast, temporal analysis of Marietas shows that the habitat is primarily shaped by physicochemical variables with herbivorous fish being mainly small farmer species related to branching corals. Notably, these closely situated insular systems present varied ecosystem mediators, influenced by diverse drivers including fish traits and environmental factors. This study underscores the potential of employing a framework of ecological species traits combined with ordination methods to unravel the distinct site dynamics that contribute to the persistence of coral ecosystems within the MTP. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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15 pages, 1561 KiB

Open AccessArticle

Size Effects on Pumping Rates in High Microbial versus Low Microbial Abundance Marine Sponges

by Michael P. Lesser

Oceans 2023, 4(4), 394-408; https://doi.org/10.3390/oceans4040027 - 30 Nov 2023

Cited by 3 | Viewed by 1442

Abstract

Sponges are increasingly recognized as ecologically important on coral reefs as scleractinian corals decline. Most sponge species can be divided into two symbiotic phenotypes which are characterized as high microbial abundance (HMA) or low microbial abundance (LMA) sponges. Sponge species of HMA or [...] Read more.

Sponges are increasingly recognized as ecologically important on coral reefs as scleractinian corals decline. Most sponge species can be divided into two symbiotic phenotypes which are characterized as high microbial abundance (HMA) or low microbial abundance (LMA) sponges. Sponge species of HMA or LMA symbiotic phenotypes differ not just in their microbiomes, but in other characteristics, including that LMA sponges actively pump at higher rates than HMA sponges based on a standard normalization to size. This dichotomy has recently been questioned because the size range of LMA sponges used to quantify pumping rates during studies on their trophic ecology were exceedingly small, often less than an order of magnitude. Here, both HMA and LMA sponges, across two to three orders of magnitude in sponge volume (mL) or mass (g) were assessed for allometric relationships between sponge size and pumping rates (Q = mL s⁻¹). The scaling analysis of all data sets combined reveals that HMA sponges scale their pumping rates isometrically with size, while LMA sponges scale their pumping rate allometrically. When HMA species are examined separately, however, tropical HMA sponges scaled isometrically, while temperate HMA sponges scaled allometrically. From an ecological perspective, to quantify differences between HMA and LMA sponges for rate functions of interest (e.g., feeding) it is important to remove the effects of size as a covariate, and adjust the Q values of sponges to a standard volume or mass. For multiple species and geographic locations, this analysis shows that LMA sponges always maintain higher Q values. On tropical coral reefs, the differences between HMA and LMA sponges are intrinsic and constrained by strong evolutionary selection resulting in fixed differences in Q, regardless of sponge size. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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10 pages, 1110 KiB

Open AccessArticle

Evidence of Sexual Reproduction in Out-Planted Coral Colonies

by Violeta Martínez-Castillo, Alma Paola Rodríguez-Troncoso and Amílcar Leví Cupul-Magaña

Oceans 2023, 4(4), 350-359; https://doi.org/10.3390/oceans4040024 - 25 Oct 2023

Viewed by 1661

Abstract

Intervention techniques to restore coral communities have become an important management tool to help recover and rehabilitate damaged reefs. The direct transplantation of healthy coral fragments is the most common method; however, there is controversy in the long-term success, as using coral clones [...] Read more.

Intervention techniques to restore coral communities have become an important management tool to help recover and rehabilitate damaged reefs. The direct transplantation of healthy coral fragments is the most common method; however, there is controversy in the long-term success, as using coral clones may diminish the genetic diversity of the coral population. Genetic recombination can be achieved when the coral colony produces gametes and eventually reproduces; therefore, it is important to provide evidence that restored colonies produce gametes as their naturally recruited counterparts with similar colony size (age). Natural and restored Pocillopora coral colonies of the same size range (between 40 and 50 cm in diameter) were tagged and sampled during the rainy season to determine gamete maturation. Our results show no differences in the reproductive activity among colonies: natural and restored coral colonies matured gametes from June to October, with a peak in sexually active coral colonies in July. Also, gamete malformation was not observed. During the gamete production period, the area’s temperature ranged from 27.9 to 30.02 °C. The results’ evidence that coral colonies formed through active restoration contribute not only to the increase in live coral cover as seen in previous studies but potentially contribute in the medium term (>5 years after out-planting) to the production of larvae and local and subsidiary recruitment, since they exhibit the same reproductive patterns as their naturally formed counterparts and no differences in the reproductive activity among coral colonies. Therefore, long-term coral restoration projects contribute to maintaining the live coral cover and the genetic diversity in the region, eventually rehabilitating the coral community. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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16 pages, 3438 KiB

Open AccessArticle

Status of Coral Reef Communities on the Caribbean Coast of Costa Rica: Are We Talking about Corals or Macroalgae Reefs?

by Fabio Quezada-Perez, Sebastián Mena, Cindy Fernández-García and Juan José Alvarado

Oceans 2023, 4(3), 315-330; https://doi.org/10.3390/oceans4030022 - 20 Sep 2023

Cited by 1 | Viewed by 3363

Abstract

In the past decades, one of the most widely reported phenomena on Caribbean reefs is the general fall in coral cover and rise in macroalgae. Reefs with low coral cover and high macroalgal abundances are often presumed to provide poorer ecosystem functions and [...] Read more.

In the past decades, one of the most widely reported phenomena on Caribbean reefs is the general fall in coral cover and rise in macroalgae. Reefs with low coral cover and high macroalgal abundances are often presumed to provide poorer ecosystem functions and services. In this study, we assessed the condition of coral reefs on the Caribbean Coast of Costa Rica and determined how eight key ecosystem metrics varied in response to different coral and fleshy macroalgae covers. Most reefs surveyed had high fleshy macroalgae and low live coral covers, with an average (±SD) of 31 ± 28% and 14 ± 13% per site. The value of many of the ecosystem metrics estimated for coral reefs of the region appears to be lower than what has been reported for other areas in the Caribbean. We found that the rugosity, urchin density, fish richness, total fish biomass, large fish density, and the potential fishery value of the reef were higher in sites with low fleshy macroalgae covers (<10%). Our results concur with the prevailing paradigm that an increase in macroalgae abundance could reduce the ecosystem services provided by coral reefs. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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15 pages, 20365 KiB

Open AccessArticle

A Demonstration of the Capability of Low-Cost Hyperspectral Imaging for the Characterisation of Coral Reefs

by Jonathan Teague, John C. C. Day, Michael J. Allen, Thomas B. Scott, Eric J. Hochberg and David Megson-Smith

Oceans 2023, 4(3), 286-300; https://doi.org/10.3390/oceans4030020 - 23 Aug 2023

Cited by 2 | Viewed by 2580

Abstract

The use of hyperspectral imaging in marine applications is limited, largely due to the cost-prohibitive nature of the technology and the risk of submerging such expensive electronics. Here, we examine the use of low-cost (<5000 GBP) hyperspectral imaging as a potential addition to [...] Read more.

The use of hyperspectral imaging in marine applications is limited, largely due to the cost-prohibitive nature of the technology and the risk of submerging such expensive electronics. Here, we examine the use of low-cost (<5000 GBP) hyperspectral imaging as a potential addition to the marine monitoring toolbox. Using coral reefs in Bermuda as a case study and a trial for the technology, data was collected across two reef morphologies, representing fringing reefs and patch reefs. Hyperspectral data of various coral species, Montastraea cavernosa, Diploria labyrinthiformis, Pseudodiploria strigosa, and Plexaurella sp., were successfully captured and analyzed, indicating the practicality and suitability of underwater hyperspectral imaging for use in coral reef assessment. The spectral data was also used to demonstrate simple spectral classification to provide values of the percentage coverage of benthic habitat types. Finally, the raw image data was used to generate digital elevation models to measure the physical structure of corals, providing another data type able to be used in reef assessments. Future improvements were also suggested regarding how to improve the spectral data captured by the technique to account for the accurate application of correction algorithms. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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6 pages, 1627 KiB

Open AccessCommunication

Novel Interaction between a Rabbitfish and Black Corals

by Erika Gress, Tom C. Bridge, Justin Fyfe and Gemma Galbraith

Oceans 2023, 4(3), 236-241; https://doi.org/10.3390/oceans4030016 - 13 Jul 2023

Cited by 1 | Viewed by 2366

Abstract

Herbivorous fishes play important functional roles in coral reef ecosystems, and their influence on mediating competitive dynamics between corals and macroalgae is well studied. Nonetheless, direct interactions between herbivorous fishes and corals may also be relevant, although these are less studied. Here, we [...] Read more.

Herbivorous fishes play important functional roles in coral reef ecosystems, and their influence on mediating competitive dynamics between corals and macroalgae is well studied. Nonetheless, direct interactions between herbivorous fishes and corals may also be relevant, although these are less studied. Here, we describe a series of observations of schools of the herbivorous streaked rabbitfish (Siganus javus) nibbling on black corals (order Antipatharia) at the SS Yongala wreck, within the Great Barrier Reef Marine Park. We provide a hypothesis that may explain this behaviour, which, if confirmed, would represent a mechanism influencing the health of the corals. Moreover, this interaction extends the typical coral–algae competition for space paradigm and furthers knowledge of complex relationships between coral reef organisms. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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15 pages, 2544 KiB

Open AccessArticle

Seasonal Upwelling Conditions Modulate the Calcification Response of a Tropical Scleractinian Coral

by Carlos E. Gómez, Andrés Acosta-Chaparro, Cesar A. Bernal, Diana I. Gómez-López, Raúl Navas-Camacho and David Alonso

Oceans 2023, 4(2), 170-184; https://doi.org/10.3390/oceans4020012 - 18 Apr 2023

Cited by 2 | Viewed by 2986

Abstract

Natural processes such as upwelling of deeper-water masses change the physical-chemical conditions of the water column creating localized ocean acidification events that can have an impact on the natural communities. This study was performed in a coral reef system of an archetypical bay [...] Read more.

Natural processes such as upwelling of deeper-water masses change the physical-chemical conditions of the water column creating localized ocean acidification events that can have an impact on the natural communities. This study was performed in a coral reef system of an archetypical bay within the Tayrona National Natural Park (PNNT) (Colombia), and aimed to quantify net calcification rates of a foundational coral species within a temporal context (6 months) taking into account the dynamics of seasonal upwelling that influence the study area. Net calcification rates of coral fragments were obtained in situ by the alkalinity anomaly technique in short-term incubations (~2.5 h). We found a significant effect of the upwelling on net calcification rates (Gnet) (p < 0.05) with an 42% increase in CaCO₃ accretion compared to non-upwelling season. We found an increase in total alkalinity (A_T) and dissolved inorganic carbon (DIC) with decreased aragonite saturation (Ω_ara) for the upwelling months, indicating an influence of the Subtropical Under Water mass (SAW) in the PNNT coral community. Significant negative correlations between net calcification with temperature and Ω_ara, which indicates a positive response of M. auretenra with the upwelling conditions, thus, acting as “enhancer” of resilience for coral calcification. Full article

(This article belongs to the Special Issue Coral Reef Ecology and Biology)

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