Echinoderm Assemblages Research Articles

Late Holocene echinoderm assemblages can serve as paleoenvironmental tracers in an Antarctic fjord

High Latitude fjords can serve as sediment trap, bearing different type of proxies, from geochemical to micropaleontological ones, making them exceptional tools for paleoenvironmental reconstruction. However, some unconventional proxies can be present and can be used to depict a comprehensive and exhaustive interpretation of past changes. Here, studying a sediment core in Edisto Inlet (Ross Sea, Antarctica) we used irregular echinoid spines and ophiuroids (Ophionotus victoriae) ossicles to trace environmental changes throughout the last 3.6 kyrs BP. Irregular echinoids can serve as proxy for the organic matter content, while O. victoriae ossicles can be used as proxy for steady sea-ice cycle along with organic deposition events. O. victoriae release a high number of ossicles, making estimation about the population quite challenging; still, presence data, can be easily collected. By applying Generative Additive Models to the stratigraphical distribution of these data, we detected an environmental phase that was previously unnoticed by other traditional proxies: the Ophiuroid Optimum (2–1.5 kyrs BP). In conclusion, here we demonstrate how echinoderm presence can be used as a valuable source of information, while proving the potential of modelling binary data to detect long-term trend in Holocene stratigraphical records.

A New Species of <i>Nucleolites</i> (Echinoidea, Cassiduloida) from the Lower Albian of Russian Plate

A new species of Nucleolites from the Lower Albian deposits (Arcthoplites jachromensis Zone) of the Pavlovskoye section (Yuriev-Polsky district, Vladimir region) was described based on eight specimens. The species characterizes the late stages of the phylogeny of the genus and significantly expands its paleogeography. The taphonomic features of the burial made it possible to trace the structure of the jaw apparatus of the cassiduloid type in adult Nucleolites. For the first time in the Albian deposits of the Russian Plate, an extensive echinoderm assemblage, which is the most representative for the Lower Cretaceous deposits of the region as a whole, was established.

Diversity, distribution patterns and indicatory potential of echinoderm communities of the tropical East Atlantic (Gulf of Guinea): Influence of multiple natural and anthropogenic factors along a 25–1000 m depth gradient

All earlier studies of the West African echinoderm fauna have focused on taxonomy, and general knowledge about benthic community responses to various human related threats are poorly diagnosed and not monitored along the whole African coast. Our analysis of diversity and distribution patterns of Ghanaian echinoderms yielded 36 species. Material was collected at nine transects distributed along the coast of Ghana (25–1000 m depth range, total of over 270 samples). Gradual decreases in species richness, diversity, evenness and abundance were observed along the depth gradient, with the most diverse fauna being recorded on the shelf (25–50 m). The most abundant species were Ophiactis luetkeni and Ophiothrix congensis, although both had very patchy distributions. Cluster analysis separated shelf communities (25–100 m) from slope communities (500–1000 m), although on a low level of similarity. Our analysis allowed to select most vulnerable benthic habitats that should be amongst priorities of the future monitoring. Local influence of arsenic was observed at some shelf sites, while slope fauna was affected by elevated levels of hydrocarbons and barium. Changes in salinity and fluorescence also influenced echinoderm assemblages. The most general trend showed patchily distributed, diverse shallow water fauna being influenced by increased microhabitat diversity and food availability, while depauperate slope fauna was affected by local disturbances associated with oil extraction. Tropical echinoderm communities have a great potential as indicators of even minor and local pollution, although high patchiness and low abundance creates difficulties in the multivariate analysis. High sampling effort and high number of replicates allowed to minimise those problems and demonstrated small scale microhabitat diversity.

Taxonomical and functional diversity dynamics of conspicuous echinoderms in the northeastern tropical Pacific over a decade

Understanding what determines spatio-temporal changes in echinoderm assemblages from an integrative perspective that considers biodiversity, species evenness, and species’ niches could permit superior community-scale characterizations of habitat resilience to disturbance. Such an approach was taken herein by tracking a Central Mexican Pacific echinoderm assemblage between 2012 and 2021, and higher richness, diversity, evenness, and functional entity counts were associated with more heterogeneous benthic assemblages. Echinoderm taxonomic composition was influenced by ENSO events, with higher functional diversity found during La Niña events. Conservation strategies should focus on species with unique functional traits to maintain the balance of coral community functionality.

New Middle and Late Ordovician cornute stylophorans (Echinodermata) from Morocco and other peri-Gondwanan areas

Abstract Cornute stylophorans are a minor, although typical, component of Middle–Late Ordovician echinoderm assemblages adapted to soft siliciclastic substrates in high-latitude peri-Gondwanan regions. All previously reported occurrences of Darriwilian–Katian cornutes from the Czech Republic, France, Morocco and Spain are revised and their plate homologies reassessed. The genera Beryllia and Juliaecarpus are reinterpreted as junior synonyms of Domfrontia , and Thoralicystis is synonymized with Bohemiaecystis . Several Mediterranean scotiaecystids previously assigned to Bohemiaecystis and/or Scotiaecystis are placed within Thoralicarpus gen. nov., and cornute taxa originally left in open nomenclature by Chauvel are formally described as Bohemiaecystis chouberti sp. nov. (AVI) and Destombesicarpus izegguirenensis gen. et sp. nov. (AVIII). Other new Mediterranean taxa include Arauricystis clariondi sp. nov., Destombesicarpus budili gen. et sp. nov., Milonicystis reboulorum sp. nov., Thoralicarpus bounemrouensis gen. et sp. nov., and T . prokopi gen. et sp. nov. The six cornute genera identified in Darriwilian–Katian Moroccan echinoderm Lagerstätten are also present in coeval assemblages of at least one other Mediterranean region, thus supporting the existence of strong faunal affinities between the Anti-Atlas, the Armorican Massif, the Barrandian area and the Iberian Peninsula.

Dominance of Miocene echinoderms in the equatorial Neogene marine platform of Brazil and their insights into the paleoenvironment

Echinoderms are one of the most important invertebrates in the early to middle Miocene heterozoan carbonate deposits of the Pirabas Formation of the northern Brazil. The well-preserved echinoid tests were useful for accurate identification, whereas the sediment filling the tests provide significant information regarding the rock matrix. The dominance of disarticulated ophiuroid, crinoid, and asteroid plates, and damage on the echinoderm test provides a basis for taphonomic processes to elucidate a paleoenvironmental interpretation based on the echinoderm assemblages. Nineteen echinoderm taxa (ten valid species and nine species in open nomenclature) were recorded based on well-preserved and/or fragmented tests and/or spines, including Abertellidae †Abertella pirabensis (Santos, 1958), Placatenellidae †Placatenella complanata (Brito, 1981), Clypeasteridae †Clypeaster lamegoi Santos, 1958, †Clypeaster paraensis Brito, 1979, and †Clypeaster paulinoi Santos, 1958, Cassidulidae †Anisopetalus oliveirai (Santos, 1958) and †Rhyncholampas candidoi Fernandes and Morais, 1994, Echinolampadidae †Echinolampas paraense Santos, 1958, Schizasteridae †Agassizia eugeniae Brito and Ramires, 1974 and Schizaster sp., Cidaridae Cidaris sp., †Phyllacanthus priscus Brito and Ramires, 1974, and Prionocidaris sp. The smaller echinoderm fragments were dominated by disarticulated plates of Gorgonocephalidae ophiuroids, Comatulidae crinoid Sievertsella sp., Goniasteridae asteroids, as well as spines and tests fragments of Cidaridae echinoids. The echinoderm assemblages suggest an inshore and shallow water paleoenvironment over a soft sandy carbonate bottom. MicroCT analyses of sediments filling echinoid tests exhibited a microfossil assemblage, including foraminifera, sponges, ahermatypic corals, bryozoans, and mollusks. Broken and disarticulated tests and plates in chaotic orientations suggest high-energy paleoenvironment. Evidence of test damage indicates complex predator-prey interactions. Overall, the microCT analyses of echinoid tests proved to be a high accuracy non-destructive, analytical approach for investigating fossil echinoderms and their paleoenvironment.

Environmental Drivers of Mesophotic Echinoderm Assemblages of the Southeastern Pacific Ocean

Mesophotic ecosystems (50–400 m depth) of the southeastern Pacific have rarely been studied because of the logistical challenges in sampling across this remote zone. This study assessed how oxygen concentrations and other environmental predictors explain variation in echinoderm assemblages at these mesophotic systems, where this group is among the predominant fauna. We compiled data on echinoderm taxa at 91 sampling stations, from historical and recent surveys (between 1950 and 2019), covering a longitudinal gradient of approximately 3,700 km along with the Nazca, Salas y Gómez, and Juan Fernández ridges. Uni- and multivariate model-based tools were applied to analyze the patterns of benthic fauna in relation to environmental factors. Our results indicate a significant positive relationship between echinoderm species richness and depth, oxygen, and salinity. Changes in echinoderm community composition were significantly explained by oxygen, longitude, and chlorophyll-a. We observed notable species turnovers at ∼101 and ∼86°W, where assemblages tend to be more variable across stations. This turnover possibly reflects the effects of physical barriers to dispersion (e.g., currents) and habitat changes. Echinoderm assemblages observed around Easter and Desventuradas Islands presented a high occurrence of potentially endemic taxa and distinct species assemblages. This study is the first to assess the structure of mesophotic echinoderm assemblages of the southeastern Pacific Ocean along a large spatial scale. The information reported here could help design appropriate management tools for the vast, recently created, marine protected areas in the southeastern Pacific.

Species assemblage and recruitment patterns of echinoderms on shallow rocky reefs in central New Zealand

ABSTRACT Echinoderms play important ecological roles in the benthic community, but the processes that regulate their distribution are still poorly understood. The aim of this study was to describe the community structure in the shallow rocky reefs of the Wellington region of central New Zealand. Five sites from a harbour and an open coast were surveyed for adult echinoderm density and habitat composition. Additionally, artificial collectors were deployed to assess recruitment patterns. Five taxa were responsible for the assemblage variation within sites and their abundance was highly correlated with habitat composition. Patiriella regularis was highly abundant in all sites, while Coscinasterias muricata and Evechinus chloroticus were dominant in the Harbour. Echinoderm settlement showed interannual variations, as well as differences between locations. There was a significant pulse of C. muricata settlers, while ophiuroids were present in lower numbers but constantly during the studied period. E. chloroticus settlement was sporadic and the absence of a juvenile cohort in the open coast sites suggests that recruitment might not occur for up to 4 years. The present study provides insights on the echinoderm assemblage in the shallow rocky reefs of the Wellington region and contributes to a better understanding of recruitment patterns shaping population structure.

Shelly fauna from the Cambrian (Miaolingian, Guzhangian) Shannon Formation and the SPICE event in the Amadeus Basin, Northern Territory

Smith, P.M., Brock, G.A. & Paterson J.R. 20 September 2019. Shelly fauna from the Cambrian (Miaolingian, Guzhangian) Shannon Formation and the SPICE event in the Amadeus Basin, Northern Territory. Alcheringa 44, 1–24. ISSN 0311-5518 A low-diversity assemblage of linguliformean brachiopods, hyoliths, molluscs, bradoriid arthropods and echinoderms (ten taxa in total) is documented from the upper Shannon Formation (Cambrian, Miaolingian, Guzhangian; Mindyallan) in the Ross River Syncline and Todd River Anticline area, NE Amadeus Basin, central Australia. Taxa described include: the linguliformean brachiopods Treptotreta jucunda Henderson & MacKinnon, 1981, Opisthotreta sp., Stittia? sp., an undetermined acrotretid and an undetermined linguloid; the molluscs Kobayashiella? heritagensis Webers, Pojeta & Yochelson, 1992 (a paragastropod), and Apoptopegma joyceae sp. nov. (a rostroconch); the bradoriid Mongolitubulus sp.; Hyolithida gen. et sp. indet.; and isolated echinoderm plates. All fauna (including previously documented trilobites) from the upper Shannon Formation disappear at the beginning of a ∼5‰ positive shift in δ13C, identified as the Steptoean Positive Isotopic Carbon Excursion (SPICE). Despite previous links between SPICE and a global extinction, as well as the disappearance of all faunal elements in the uppermost Shannon Formation, certain taxa reported herein range through the event elsewhere in the world. The occurrence of Treptotreta jucunda and Kobayashiella? heritagensis in younger (Furongian) deposits indicates these species survived the SPICE extinction event. This study advocates for more systematic and comprehensive sampling through stratigraphic intervals where the SPICE event occurs, especially for range data of complete faunas (rather than individual taxonomic groups), to facilitate a more complete picture of diversity trends through this important phase. P.M. Smith* [patrick.smith@austmus.gov.au], Palaeontology Department, Australian Museum Research Institute, Sydney, New South Wales, 2010, Australia; G.A. Brock [glenn.brock@mq.edu.au], Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia. J.R. Paterson [jpater20@une.edu.au], Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, 2351, Australia. *Also affiliated with: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

Spatial-temporal variations in echinoderm diversity within coral communities in a transitional region of the northeast of the eastern pacific

Echinoderms associated with coral communities in the Easter Pacific compose a conspicuous assemblage that alters their ecosystem structure and composition. The environmental conditions in the transitional region of Central Mexican Pacific (CMP) present high variability associated with climatic seasons and El Niño-Southern Oscillation (ENSO) events. In order to understand it, a research was held during four years (2011-2014) throughout the CMP region with seven conspicuous echinoderm indicator species. Echinoderms diversity, distribution, and density were measured, and also their relation with benthic coverage, depth, rugosity, and temperature. The echinoderm assemblages changed in density and diversity among localities and regions over the years. Their presence was positive related with the occurrence of algal turf and corals, but absent in the presence of coral rubble and fleshy macro-algae. Also, during the negative phase of ENSO/2011, the increase of algal turf favored the abundance of echinoids. Subsequent to ENSO, their density decreased but the richness of the echinoderm assemblage remained stable, suggesting that coral communities in the study area possess a strong resilience, where local abiotic and biotic factors maintain a dynamic balance in echinoderm populations.

Quantification of echinoderms (Echinodermata) on Georges Bank, and the potential influence of marine protected areas on these populations

AbstractThe spatiotemporal variation of the distribution of echinoderms in the Georges Bank ecosystem was examined from 2005 to 2012. Density and abundance of representatives from echinoderm classes (brittle stars, sand dollars, sea stars, and sea urchins) were estimated using a drop camera video survey of the benthos in areas open and closed to fish trawling. The influence of closed areas on these echinoderm populations relative to a suite of key environmental and biotic factors was evaluated using Canonical Correspondence Analysis (CCA). While marine protected areas appeared to influence the distribution of sand dollars and sea stars, the distribution of brittle stars and sea urchins seemed to be defined mainly by preferred habitat conditions. According to the CCA, depth, sediment stability, temperature, predator abundance, and management area were the most important factors explaining this echinoderm assemblage. On Georges Bank, echinoderms dominate the benthic biota and are present in a variety of habitats. They can alter marine communities and are preferred prey and main predators for several commercially targeted species. The detailed information presented here (on the scale of kilometers) on abundance and spatial distribution of these populations is thus valuable towards the implementation of ecosystem‐based fisheries management.

TAPHONOMY AND PALEOECOLOGY OF AN OPHIUROID-STYLOPHORAN OBRUTION DEPOSIT FROM THE LOWER DEVONIAN BOKKEVELD GROUP, SOUTH AFRICA

The taphonomy of a well preserved ophiuroid-stylophoran assemblage from the Bokkeveld Group, Lower Devonian of South Africa is described using micro-CT scanning techniques. This assemblage provides a taphonomic window into the structure of Early Devonian, echinoderm-dominated communities within the Malvinokaffric Realm of SW Gondwana. Micro-CT scanning and 3D modeling of a portion of an obrution bed revealed an assemblage of over 700 ophiuroids observed of the newly described Gamiroaster tempestatisReid 2019 associated with two species of stylophorans of two species, the mitrates Paranacystis cf. petriiCaster 1954 and Placocystella africana (Reed 1925). The 3D model permitted detailed sedimentologic and taphonomic analysis of the bed including determination of the degree of fossil articulation, orientation, and faunal counts. The results indicate that deposition took place in a storm-influenced, shallow marine environment smothering both attached and vagrant taxa of the benthic community during a high-energy storm event. Micro-CT scanning is a powerful taphonomic tool for the non-destructive analysis of delicate echinoderm assemblages that would otherwise be difficult to study.

Une nouvelle perspective dans l'étude des crinoïdes (Crinoidea, Echinodermata) : Un exemple du Jurassique inférieur du Monténégro

Lower Jurassic (Hettangian-Pliensbachian) shallow-marine ooidal limestones of southern Montenegro contain a large number of isocrinid ossicles. They are assigned to the following taxa: Isocrinus psilonoti (Quenstedt), Isocrinus sp., and Pentacrinites cf. fossilis Blumenbach. The echinoderm assemblage also yields cyrtocrinid ossicles (Cotylederma sp., Cyrtocrinina indet.) and echinoid spines (only spotted in thin sections); however, these elements are rare. Given the fact that the recorded assemblage comes from a single locality, there is a growing need for further research that will require intense sampling to compile and complete the faunal list of crinoids and other echinoderm taxa.

Conventional MPAs are not as effective as community co-managed areas in conserving top-down control in the Gulf of California

While undeniably successful in protecting nearshore marine ecosystems from overfishing, conventional marine reserves often impinge on the livelihoods of dependent coastal communities. Community co-managed areas may guarantee considerably more equity, but it is unclear if they can be as effective as conventional reserves in conserving critical trophic functions. We evaluated the effectiveness of different management regimes in the Gulf of California on fish biomass and echinoderm assemblages as proxies of key ecosystem processes on rocky shores. We compared multiple sites in a mixed (multi-use areas with regulated extraction) and core (no-extraction) federally-managed areas, a military MPA (where strict patrolling ensures no extraction), a co-managed reserve where government and communities are equally responsible, and unrestricted-access areas (non MPA). Fish biomass was higher in the military reserve and the community co-managed area reserve; echinoderm numbers were very low at these locations suggesting that they were strongly controlled by top-down processes. In contrast, federally-controlled reserves were virtually no different from unrestricted-access areas in numbers or composition of fish and echinoderms. Although federal managed reserves are the most common management regime across the Gulf, our data shows that they are highly ineffective in protecting ecosystem function. The relative effectiveness of co-managed reserves in this region suggests that fishers are more willing to comply when they have a stake in decision-making. Coastal conservation can benefit greatly by drawing from a wider suite of management options that engage local communities as key participants in the managing marine diversity and critical ecosystem functions.

An echinoderm Lagerstätte from the Upper Ordovician (Katian), Ontario: taxonomic re-evaluation and description of new dicyclic camerate crinoids

AbstractThe Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region of Ontario contain a highly diverse echinoderm assemblage that is herein recognized as a Konservat-Lagerstätte. Although fossil crinoids have long been recognized from these formations, the fauna has not received a comprehensive taxonomic evaluation since Springer’s classic 1911 monograph. Recent extensive collection and preparation of new material from the Bobcaygeon and Verulam formations near Brechin, Ontario recovered numerous exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. The Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna, with more than 20 crinoid genera represented in this collection.Here, all dicyclic crinoids belonging to subclass Camerata from the Brechin Lagerstätte are evaluated. The following four genera and seven species are described from the fauna, including one new genus and four new species:Reteocrinus stellaris,Reteocrinus alveolatus,Archaeocrinus sundayaen. sp.,Archaeocrinus maraensisn. sp.,Priscillacrinus elegansn. gen. n. sp.,Cleiocrinus regius, andCleiocrinus lepidotusn. sp. The exceptional preservation of this collection provides an opportunity to describe more fully the morphologic and ontogenetic details of known Ordovician crinoid taxa, to conduct a taxonomic re-evaluation of many species, to describe new taxa, and to provide a framework for subsequent studies of crinoid community paleoecology.UUID:http://zoobank.org/e3e268a7-88e5-43cd-84ea-b40df45e8281

Distribution and abundance patterns of echinoderms in the fjord and channel complex from a subantarctic north Patagonian Ice field, Magellan region

The existence of latitudinal marine biodiversity gradients from low to high-southern latitudes is a controversial issue regarding the marine biogeographic division in the Southeastern Pacific. In this region, the Northern Patagonian Icefield is considered a break point for faunistic elements derived from more northern or southern biogeographical realms. However, the division seems to be better defined by distribution patterns and endemism of specific marine taxa. There have been no exhaustive latitudinal benthic inventories compiled along the southern-eastern Pacific Chilean coastline. This study focuses on the spatial distribution variability and relative abundance of the sublittoral echinoderm assemblages and uses them to establish an evaluation of zoogeographic relationship in the Southeastern Pacific and Atlantic Oceans. This is the first time echinoderms have been used for this purpose. A total 3 665 echinoderm specimens were collected in two cruises. Within this organism pool, 29 species were distinguished, belonging to the asteroids (17 species), echinoids (6 species), ophiuroids (4 species) and holothurians (2 species); crinoids were not found. The dominant species were the asteroid Ctenodiscus procurator, the echinoid Pseudechinus magellanicus, the ophiuroid Ophiuroglypha lymani, and the irregular sea urchin Tripylaster philippii. The spatial distribution patterns for the echinoderm clusters along the study area showed only weak geographical trends. Stations belong in three groups: with influence of glacier processes, influence of waters of the open Pacific Ocean, and a third group of stations without any links to specific locations. Rev. Biol. Trop. 65(Suppl. 1): S60-S72. Epub 2017 November 01.

Primitive stalked echinoderms from the Middle Ordovician (Darriwilian) of Bang Song Tho, Kanchanaburi, western Thailand

AbstractThe Middle Ordovician (Darriwilian) echinoderm fauna of Bang Mueang Song Tho, western Thailand (Pha Phum group, Bo Ngam Formation(?)), includes rare thecae, and common thecal ossicles and columnals, and is dominated by ‘cystoids’. Cheirocrinid glyptocystitoids includeCheirocystellasp. (=Echinoencrinitessp. aff.E. senckenbergii(von Meyer)sensuWolfart), ‘Cheirocrinus’ sp. and Cheirocrinidaeincertae sedis. Hemicosmitoids are composed ofParacaryocrinites kochi(Wolfart), ‘Paracaryocrinites’ sp. andPolycosmitessp. cf.P. kaekeliWolfart. The aristocystitidSinocystissp. cf.S. loczyiReed is the only diploporite. Columnals ofBystrowicrinus(col.) sp. are probably crinoidal. The fullest determination of the echinoderm biodiversity of this site has been obtained using all specimens from single ossicles to articulated thecae. The limited taphonomic data suggests that the echinoderm assemblage is parauthochthonous. Other echinoderms described from coeval deposits in this region includeStichocystis thailandicaWolfart;Heliocrinitessp. aff.H. qualusBather (probably aLophotocystisPaul);Gomphocystites? sp. indet. (= trilobite?);Codiacystissp. aff.C. bohemicus(Barrande) (= bryozoan?);Aristocystis[sic] sp. A of Paul; and [non]Incertae sedissp. C of Paul (may not be an echinoderm).

PALEOECOLOGY OF ECHINODERMS IN COLD SEEP ENVIRONMENTS REVEALED BY ISOTOPE ANALYSIS IN THE LATE CRETACEOUS WESTERN INTERIOR SEAWAY

A cold seep is an extreme environment characterized by a specialized group of organisms generally referred to as “chemosynthetic communities”. Until recently, echinoderms were thought to be rare in cold seep environments and had not been treated as a member of chemosynthetic communities, which otherwise are composed of a variety of taxa. One fossil echinoderm assemblage associated with a cold seep comes from the middle Campanian Pierre Shale Formation of the U.S. Western Interior Seaway. In this study, the taxonomy, morphology, and paleoecology of fossil echinoderms (crinoids and echinoids) from the Pierre Shale are discussed. Elemental chemical analyses of the fossil echinoderm skeletons and stable carbon isotopes were used to clarify the influence of seep hydrocarbons chemistry on the formation and diagenesis of echinoderm skeletons. We show that the crinoids Lakotacrinus brezinai from seep carbonates developed highly specialized morphologies and skeletons with low δ 13 C values, suggesting that it was adapted to cold seep environments and might be an obligate member of the chemosynthetic community. The echinoids from the Western Interior Seaway seep carbonates have morphologies and skeletal δ 13 C values not significantly different from those from non-seep environments, suggesting that the echinoids were not obligate members of the chemosynthetic community, but opportunists living in the periphery of the cold seep habitat.

Structural and environmental effects on an assemblage of echinoderms associated with a coral community

Echinoderms are a conspicuous assemblage associated with coral communities, which provides them with food, shelter, and nursery areas. Temporal and spatial changes in environmental conditions may modify their density and composition, which furthermore may affect the structure of the coral community. In order to identify the response of echinoderm composition to environmental fluctuations, variations in the density were evaluated at spatial and temporal levels from 2011–2014 in Islas Marietas National Park, a National Protected Area located off the Mexican Pacific coast, which harbors the most important coral and echinoderm community in the region. The results showed that the species Diadema mexicanum, Centrostephanus coronatus, and Eucidaris thouarsii, were dominant. Differences between areas off the islands were observed, as Isla Redonda showed the highest values (1.31 ± 0.15 in. m2, \( \overline{S} \) = 7.74 ± 0.17) associated with high heterogeneity and availability of food resources. Isla Larga had the lowest density (0.89 ± 0.7 in. m2) and richness (\( \overline{S} \) = 6.49 ± 0.24). This was associated with the presence of high coverage of branching corals (16.34%) which can be considered a space competitor for echinoderms. Moreover, during cold seasons, density (17.44%) and richness (12.6%) increased, with a positive relation with the food supply. During the 2011/La Nina, a partial coral mortality resulted in the proliferation of turf and contributed to the highest abundance of grazer echinoderms. Abundance decreased during the following years, due to the loss of turf coverage. The assemblage of echinoderms maintained their species composition over the years, showing that the coral community of the Central Mexican Pacific has a singular auto-regulatory capacity that allows their long-term maintenance in response to environmental anomalies.

Influence of the coral reef assemblages on the spatial distribution of echinoderms in a gradient of human impacts along the tropical Mexican Pacific

Fourteen species of echinoderms and their relationships to the benthic structure of the coral reefs were assessed at 27 sites—with different levels of human disturbances—along the coast of the Mexican Central Pacific. Diadema mexicanum and Phataria unifascialis were the most abundant species. The spatial variation of the echinoderm assemblages showed that D. mexicanum, Eucidaris thouarsii, P. unifascialis, Centrostephanus coronatus, Toxopneustes roseus, Holothuria fuscocinerea, Cucumaria flamma, and Echinometra vanbrunti accounted for the dissimilarities among the sites. The spatial variation among the sites was mainly explained by the cover of the hard corals (Porites, Pocillopora, Pavona, Psammocora), different macroalgae species (turf, encrusting calcareous algae, articulated calcareous algae, fleshy macroalgae), sponges, bryozoans, rocky, coral rubble, sand, soft corals (hydrocorals and octocorals), Tubastrea coccinea coral, Balanus spp., and water depth. The coverage of Porites, Pavona, and Pocillopora corals, soft coral, rock, and Balanos shows a positive relationship with the sampling sites included within the natural protected area with low human disturbances. Contrary, fleshy macroalgae, sponges, and soft coral show a positive relationship with higher disturbance sites. The results presented here show the importance of protecting the structural heterogeneity of coral reef habitats because it is a significant factor for the distribution of echinoderm species and can contribute to the design of conservation programs for the coral reef ecosystem.