Discovering the Bathylithology and Bioengineering Organisms of the Punta Coles Marine Natural Reserve, Moquegua, Peru

Abstract

The Punta Coles Natural Reserve (PCNR), located on the southern coast of the province of Ilo, Moquegua Region, Peru, houses an area rich in marine biodiversity which is composed of natural banks of benthic invertebrates, which constitute the potential and dynamic fishery of commercial interest for artisanal fishermen that impact the area. To mitigate this impact, all stakeholders need to know, understand, value, and balance the dependence of benthic biodiversity with the ecosystem for its preservation and the promotion of sustainable fishing. Along these lines, the components studied are bathymetry, lithology, and the tapestry of bioengineers that make up the reserve’s seabed. Mapping of the complexity of the benthic habitat of the seabed was developed on the basis of an integrated analysis of multibeam bathymetric data, geoscientific information associated with the antecedents of benthic biodiversity of the PCNR, sediment maps of the seabed, subtidal sedimentological texture, and photographic records. The characterization and granulometry of the sediments that make up the PCNR were determined according to the Udden–Wentworth classification criterion (Φ). The utility of the GPSMAP 178C multibeam echosounder for the interpretation of seabed sediments stands out. The kriging interpolation method was used to extrapolate the characteristics of the benthic habitat, which is suitable for large areas of the sea. As a result, three habitats were derived and mapped, and three structures (bioengineers), namely, “subtidal kelps” (Lessonia trabeculata), “mussels” (Aulacomya atra), and “red sea squirt” (Pyura chilensis), were associated mainly with sedimentary rock habitats and mixed substrates. In the sand substrate, these algae were found to a lesser extent. The results show that this study is a conceptual model that summarizes the understanding of ecology and prospects for the sustainability of profitable, ecoefficient fishing activities in the Moquegua Region, Peru.

1. Introduction

There are 232 marine ecoregions organized in 62 provinces and 12 domains worldwide [1]. The coasts of Peru belong to the Guayaquil, Central Peru, and Humboldtian ecoregions, which are characterized by their geomorphology and oceanography, including upwellings, shallow areas, and mangroves [2,3]. These areas of bathilithological diversity give rise to enormous biodiversity, constituting an ecological and economic wealth that contributes 22% of the national gross domestic product (GDP) [4,5]. Therefore, preserving this ecological heritage through the establishment of natural reserves such as Punta Coles (PCNRs) is imperative [6]. Marine reserves have emerged as fundamental instruments for the conservation of biodiversity, the sustainable management of marine ecosystems [7,8,9,10,11] and the mitigation of the effects of climate change [12,13,14,15,16].

The PCNR comprises a marine and terrestrial surface of 3000 hectares. High biological diversity is represented by guano birds, South American sea lions, and diverse hydrobiological resources, some of which act as ecosystem bioengineers [17]. Key structural species include “subtidal kelps” (Lessonia trabeculata Villouta and Santelices, 1986), mantles of “mussels” (Aulacomya atra Molina, 1782), “red sea squirt” (Pyura chilensis Molina, 1782), and barnacle structures (Balanus laevis Bruguière, 1789) [18]. These species perform significant ecological functions as habitat formers [19,20,21,22,23], increasing local diversity by providing protection against predation, shelter from bottom currents, feeding grounds, reproduction sites, larval settlement areas, and invertebrate assemblages [24,25,26,27,28,29,30].

The high productivity and diversity of the Peruvian Sea [3,31,32] face significant threats, including climate change, pollution, and the overexploitation of marine resources [33,34,35,36,37,38], all of which can lead to a decline in local biodiversity [2]. For example, in the PCNR, illegal fishing, such as the harvesting of false abalone, red sea urchins, and limpets, has reduced local populations and disrupted the balance of associated communities because of the inability of stakeholders in the involved sectors to implement an effective protection program [39]. Moreover, the impacts of climate variability, such as the El Niño–Southern Oscillation (ENSO) event, which reduces upwelling and primary production and generates sea surface temperature anomalies (SSTAs), have led to a decline in the abundance of some commercial resources and ecosystem bioengineers, such as mussels and kelp beds, and, under extreme conditions, have led to massive mortality [40,41,42]. Additionally, the proximity of the PCNR to Pozo Lisas, the main beach of the Ilo Province, makes it susceptible to pollution caused by large amounts of waste (plastic bottles, food scraps, etc.) left by tourists, especially during the summer season. On several occasions, local authorities have been unable to respond promptly, which may negatively affect water quality and habitat, as described for other coastal regions [43,44].

These factors pose significant threats to the ecological health of PCNR, highlighting the critical importance of studies such as this one. Despite progress in mapping these environments, there remains a significant gap in the literature regarding the integration of bathymetric and lithological data from the PCNR seabed with the distribution of structural organisms essential for marine habitat formation and maintenance [45,46]. Since the establishment of the PCNR, only four studies have been published on its biodiversity. Two studies focused on the distribution and behavior of avifauna [47,48], whereas others examined the abundance and composition of benthic communities in the PCNR [49,50]. This limited body of research highlights the need for a more comprehensive understanding of the spatial distribution and ecological roles of key habitat-forming organisms in the reserve.

To address this research gap, our study contributes to the broader ecological and conservation framework through integrative approaches that link the habitat characteristics of the PCNR. While previous research has focused primarily on avifauna and structural species, we integrate bathymetric, lithological, and biological data to create a holistic view of the PCNR. By employing interpolation techniques and species distribution modeling, we aim to predict the distributions of structural organisms that are vital for the health and resilience of marine ecosystems [51]. This approach is particularly relevant for the unique reserve of southern Peru since it is crucial for the maintenance of the ecosystem and existing biodiversity. According to the National Service of Natural Areas Protected by the State SERNANP (RP No. 048-2016-SERNANP), the development of sustainable activities within the PCNR is oriented to the management and sustainable use of resources on the basis of the implementation of technical regulations and adaptive management criteria that ensure their long-term conservation. Furthermore, it is essential to promote environmental awareness activities and ecotourism, promoting an approach that integrates economic development with the protection of ecosystems, thus ensuring the stability of conservation elements.

2. Materials and Methods

The work was carried out in the laboratory of the Professional School of Fisheries Engineering and School of Environmental Engineering of the National University in Peru. The research was carried out for a period of eight months during 2023.

2.1. Study Area

The study area corresponds to the area of Punta Coles, which is located at approximately 17°42′ S latitude and 71°22′ W longitude and belongs to the National Reserve System of Islands, Islets, and Guaneras (RNSIIPG), which is located south of the city of Ilo in the Moquegua Region of Peru.

2.2. Collection of Bathilithological Information

To characterize the geomorphology of the seabed relief of the selected area, bathymetric surveys were carried out aboard a 5Tn artisanal vessel via the echo sounder (Echomap UHD plus 62cv, USA), which integrates GPS (South Galaxy G1, USA) and sounding functions for data collection. with semiautonomous hook-up diving dives and a review of the bibliographic information of the identification and delimitation of natural banks on the southern coast [18]. Information gathering by diving was carried out through equidistant transects (100 m) perpendicular to the coastline, establishing a total of 18 transects (Figure 1).

During the sampling in each transect, a scientific diver traveled a marked headland at 10 m intervals, recording the depth at each point and describing the habitat according to the standards established by Smith et al. [27] for the monitoring of marine habitats. The predominant type of substrate was determined in situ via the following criteria: sand (1), rock (2), and mixed (3) (Figure 2), in line with the National Oceanic and Atmospheric Administration (NOAA) protocol [51] for the classification of marine substrates. In addition, the main habitat structuring organisms, such as L. trabeculata (1), A. atra (2), and P. chilensis [3], were documented following the guidelines of Jones et al. [17] for the identification of key species.

Geographical positions were recorded via the Datum WGS84 projection. The characterization of the subtidal sedimentological texture was based on the information obtained by diving and photographic documentation of each transect, validated according to the Udden–Wentworth classification (Φ), following the Folk method [52].

2.3. Data Processing

The data were reclassified according to the geomorphological characteristics of the area (slope, orientation, and roughness) derived from the digital bathymetric model (MBD), as established in Shepard [53], for the analysis of marine surfaces.

Finally, a digital stratigraphic model (MED) was generated, exported in raster format (TIFF, ASC) with a resolution of 5 m, and aligned with the MBD according to the procedures recommended by the OGC [54]. All information processing was performed via MapSource and ArcGIS software [55] guidelines for geospatial data management.

All information processing was performed via MapSource version 6.16.3, ArcGIS Desktop 10.5, and Maxent software version 3.4.3 in accordance with ESRI guidelines [55] for geospatial data management.

3. Results

3.1. Bathilithological Survey

The sampling results revealed that the dominant substrate at Punta Coles was “rocky”, which was located mainly in shallower areas below the 15 m isobath. The “mixed” substrate (heterogeneous, composed of sand deposits and lithic outcrops) presented a relatively high proportion in the central area of the PCNR and in the vicinity of the rocky island. Moreover, the sandy substrate was located mainly in areas adjacent to Pozo Lizas beach and in deeper areas from the 30 m isobath (Figure 2A).

The width of the rocky platform in the sector in front of the “Guardianía” was approximately 300 m, whereas in the central area, in front of the Lighthouse, it reached 1000 m. In the southern area, adjacent to the Pozo Lizas beach, the rocky coverage presented an extension of less than 100 m. This habitat is closely associated with the distribution of the main benthic resources of commercial interest, such as false abalone, limpet, red sea urchin, mussels, snails, and chitons (Figure 2A).

The mixed substrate presented a discontinuous distribution, forming patches of little extension except for the rocky area in front of the lighthouse, characterized by the presence of hydrobiological resources of interest, such as clams, crabs, and octopus.

3.2. Main Habitat-Structuring Organisms

In the PCNR, a series of habitat structuring organisms can be found, the main ones being “subtidal kelps” L. trabeculata, “mussels” A. atra and the “red sea squirt” P. chilensis (Figure 2).

Figure 3 shows the different groupings recorded, revealing a predominance of mussel A. atra mantles, which were mainly distributed in deep areas above the 10 m isobath and in areas surrounding the rock island. The P. chilensis–L. trabeculata association dominated mainly in the northern area of the PCNR, from the 10 m isobath to shallower areas.

3.3. Lithology and Patches of Bioengineering Organisms

From the sampling, associations such as A. atra and L. trabeculata, which were predominantly concentrated in the central–southern rocky area of the PCNR in front of the Lighthouse sector and in areas surrounding the island, were also determined. P. chilesis and L. trabeculata were recorded in patches in the northern and central areas of the PCNR (Figure 4). The areas dominated by L. trabeculata without other prominent species presented an increase in coverage from the southern area, adjacent to Pozo Lizas beach, to the area called Guardianía. Moreover, Semimytilus patagonicus Hanley, 1843, a black mussel, and aggregations of porifera appeared in small patches scattered throughout the area and at variable depths. Likewise, the nuclei of areas without significant coverage of benthic organisms (bare rock or white background) were recorded mainly to the southwest of the PCNR (Figure 5).

Similarly, during the different tours in the different transects, a series of organisms of commercial importance and predators associated with the different habitats and substrate-forming organisms were recorded (

Table 1. Organisms of commercial importance and predators in Punta Coles.

Function	Species	Common Name	Habitat
Benthos of commercial importance	Concholepas concholepas Bruguière, 1789	False abalone, Barnacke rock shell	It was observed mainly in shallow areas, at depths less than 10 m, with rocky substratum, inhabiting cracks and vertical rocky walls, in P. chilensis matrices and among the algae L. trabeculata.
	Loxechinus albus Molina, 1782	Red sea urchin, Green sea urchin	It was recorded mainly in shallow areas with rocky substrate, at depths less than 10 m, forming aggregations or solitary, feeding on the remains (fronds) of L. trabeculata algae and calcareous algae. It was also found in areas without coverage (white backgrounds).
	Thaisella chocolata Duclos, 1832	Chocolate rock shell	It was recorded in deep areas with rocky substratum, more than 12 m deep, forming aggregations, each called an “egg cup”, or solitary on the matrices of A. atra.
	Fissurella latimarginata G. B. Sowerby I, 1835	Black limpet	It presented a bathymetric distribution similar to that observed for L. albus, concentrating on shallow areas with rocky substrate and associated with the disks of L. trabeculata.
	Fissurella pulchra G. B. Sowerby I, 1834 Fissurella cumingi Reeve, 1849 Fissurella maxima G. B. Sowerby I, 1834	Limpet	They presented a bathymetric distribution similar to that observed for F. latimarginata, recorded in the rocky substrate and associated with red calcareous algae and B. laevis barnacles.
	Romaleon setosum Molina, 1782	Rock-crabs, cancer crab	It was recorded both in rocky substrates and in soft bottoms (sandy), at depths that ranged from 5 m to 15 m, in groups or alone.
Predators Competitor	Heliaster helianthus Lamarck, 1816	Sea sun	It was recorded mainly in deep rocky areas, between 12 and 18 m deep, feeding in groups or alone on the matrices of A. atra, as well as other small mollusks and barnacles.
	Stichaster striatus Müller and Troschel, 1840	Starfish	It was recorded in shallow rocky areas, at depths less than 10 m, solitary or forming aggregations, feeding mainly on small bivalves and barnacles.
	Arbacia nigra Molina, 1782	Black sea urchin	It presented a wide bathymetric distribution, with the greatest abundances in shallow rocky areas devoid of cover, where it formed aggregations and shared habitat with L. albus. It was also recorded feeding on the stipe and fronds of L. trabeculata.

).

4. Discussion

The type of substrate, combined with the action of bioengineering organisms, plays a fundamental role in the configuration of the marine substrate, which directly affects the colonization [56] and composition of benthic communities in rocky reefs [57]. The nature of the substrate—rock, sandy, muddy, or coral—is a determining factor that influences the diversity and density of organisms in a specific area, and understanding these processes is crucial for the effective conservation of species and the sustainable management of marine protected areas [17]. Likewise, the colonization of these bioengineering species is influenced by changes in environmental conditions [58,59]. A limitation in benthic communities is free space, which can be produced by events such as El Niño, as well as by predation of the sea urchin, which implies changes in habitat recolonization [60,61,62,63].

The study of the subtidal habitat presents challenges due to its characteristics and the inherent limitations of sampling, which complicates the precise determination of the distribution of species [64]. However, various methodologies have been developed that facilitate the mapping of these complex habitats [65]. In the PCNR, autonomous diving was used for the characterization of the area [66], which allowed for the collection of data necessary for the modeling of the habitat, in addition to differentiating and delimiting the different types of habitats present, providing decision-makers with a valuable tool to improve the planning and management of management actions within the reserve.

The results of this study emphasize the predominance of the rocky substrate in the shallow areas of the PCNR, which coincides with previous observations that rocky substrates are typical in the intertidal and shallow subtidal zones of other marine ecosystems [66]. This predominance directly affects biodiversity in the region, since rocky substrates tend to support a greater diversity of organisms due to the variety of habitats they offer. On the other hand, the presence of sand, which is limited to the southern area near Pozo Lizas beach and in deeper areas, indicates local variations in sedimentary dynamics, which could be influenced by currents and waves [67]. The north and west of the Natural Reserve are characterized by rocky substrate and experience less impact from waves than the south, which is characterized by greater impact and accumulation of sand due to the intense action of waves.

The identification of the mussel A. atra, the red sea squirt P. chilensis, and the subtidal kelp L. trabeculata as the main habitat formers in Punta Coles coincides with previous studies that highlight the importance of these organisms in the structuring of marine communities [19,20,21,22,23,61]. A. atra, located mainly in deep areas, could be favored by environmental stability and the availability of nutrients, which are determining factors in the distribution of bivalves [62,63]. The association of P. chilensis with L. trabeculata, which dominates the northern area of Punta Coles from the 10 m isobath to shallower areas, suggests a preference for more dynamic conditions, where the interaction between these organisms facilitates the creation of complex habitats that support high biological diversity [64]. The nature of a protected area, where exploitation is carried out through capture limits, with a reduction in fishing efforts, allows the ecosystem to be more resilient and stable [68] and can play a role in mitigating the effects of climate change, such as macroalgae [69,70]; macroalgae forests in Chile are more abundant in protected areas than in free areas [71].

The differentiated distribution of these habitat-forming organisms indicates that environmental factors such as the depth and type of substrate play crucial roles in community structuring in Punta Coles. This pattern is similar to those identified in other studies in marine systems where the depth and variability of the substrate influence the composition and structure of biological communities [65]. For example, the greater abundance of A. atra at depths greater than 10 m could be related to less competition and predation, which are more intense in shallow waters [65].

In addition, the association of P. chilensis and L. trabeculata in the shallow areas north of Punta Coles highlights the role of these organisms as ecosystem engineers, since they not only create three-dimensional habitats that support a great diversity of species but also contribute to the stability of the substrate in high-energy areas [64]. The dominant presence of this association in shallow areas could reflect the greater adaptability of these species to the dynamic conditions generated by currents and waves in these areas.

These findings underscore the need for specific conservation approaches that recognize the importance of substrates and habitat-forming organisms in the resilience of marine ecosystems [68]. The prevalence of the rocky substrate and the presence of key species such as A. atra, P. chilensis, and L. trabeculata highlight the importance of strengthening conservation measures in these areas. This is essential to preserve the integrity of the habitat structure and, therefore, to maintain the biodiversity that these areas harbor [12,13]. The protection of these ecosystems not only ensures the survival of emblematic species but also contributes to the resilience of the marine environment against environmental pressures and human activities [10,72]. In addition, it is essential to implement monitoring programs that consider the spatial and temporal variability in the distributions of these organisms to guarantee the long-term conservation of these ecosystems. Likewise, it is advisable to promote sustainable tourism and environmental education to promote the conservation of this marine protected area, ensuring the integrity of its ecosystems and the well-being of the local communities that depend on them [73,74].

The establishment of the RNP has shown favorable results in benthic resource fisheries [8]. Since 2019, work has been conducted with a limited effort to establish capture limits for octopus and sea urchin resources. This has allowed for the maintenance of their populations as well as other resources [39], as well as an economic benefit for the extractors who have also implemented self-management actions for the best use of resources [75], in addition to having different perceptions according to their knowledge of the characteristics of the habitat and its resources, discussing among the extractors’ fishing seasons, area rotation, and catch limits per vessel, among others [76,77].

5. Conclusions

The results of the study show that the dominant substrate in Punta Coles is rocky, concentrated in shallow areas, where the use of benthic resources is carried out by local extractors, whereas the sand substrate is restricted to the southern area near Pozo Lizas beach and in deeper areas. The main organisms that form habitats in this area are “mussels” A. atra, the red sea squirt P. chilensis, and the “subtidal kelps” L. trabeculata. A. atra is found mainly at depths greater than 10 m, whereas the combination of P. chilensis and L. trabeculata dominates in the northern sector of Punta Coles, from the 10 m isobath to the shallow areas. Greater knowledge of this area will allow us to reach management proposals that consider the rotation of areas during harvesting and establish intangible areas for their conservation.