Biodiversity

Thesis Report

Coastal lagoons are rich in biodiversity and offer various ecosystem services. The close relation to the terrestrial ecosystems causes coastal lagoons to be vulnerable to impacts that are caused by human activities on land. The state of the coastal lagoons and the impact of human activities, is unknown for the Wider Caribbean Region. This study analyzes nitrate (N), phosphate (P), heavy metals, sedimentation rate and diatoms to reconstruct the recent development of four coastal lagoons in the Caribbean. Diatoms are used as proxy as they quickly respond to changes in water quality. Using short sediment cores, for four lagoons human impact is assessed. The lagoons have varying degrees of impact, from high (Fresh Pond, Sint Maarten), to medium (Spanish Lagoon, Aruba; Santa Martha, Curacao) to low impact (Saliña Bartol, Bonaire). Surface sediment samples were collected from eleven additional sites to provide a spatial context. Expected was that 1) levels of N, P, and heavy metals increase with increased human impact, that 2) biodiversity increases with decreasing human impact, and that 3) diatoms are a valuable and useful proxy for reconstructing water quality and environmental conditions. Results of heavy metals and N and P impact show that indeed human impact is most strongly pronounced in the site that was selected as high impact site (Fresh Pond, Sint Maarten). The medium and low impact sites do not show clear signs of human impact. Furthermore, results show that there is no correlation between diatom diversity and P, Chromium (Cr), Copper (Cu), and Nickel (Ni) concentrations. Although the Zinc (Zn) concentrations seem negatively correlated with diatom diversity, this is mainly caused by the low diversity of diatoms in the ponds on Sint Maarten. Observed diatom diversity is influenced by dissolution of diatom valves. Poor diatom preservation can bias results. As alkalinity, salinity and morphology of diatoms can strongly influence preservation, these factors are analyzed. Data suggests that species that are morphologically robust are less susceptible to dissolution in hyper saline conditions. A comparison of diatom assemblage between modern and sediment surface samples show that differences in observed diatom assemblage are substantial.

Coral reefs in the Atlantic have received less attention with regard to marine biodiversity research than those in the Indo-Pacific. In an overview of articles about corals or coral reefs in the journal Marine Biodiversity and its predecessor Senckenbergiana Maritima over the years 1969–2013, 35 papers concerned the Indo-Pacific and only 13 were about the Atlantic, a ratio of 2.7/1 (Hoeksema and Van der Meij 2013). Caribbean coral reefs also deserve biodiversity research attention because not all of their species have been reported yet, and these species are likely to participate in hitherto unknown interspecific associations (e.g., Thomas and Klebba 2007; Snijders and Fransen 2010; Ivanenko et al. 2017; Montano et al. 2017b) or appear to have incomplete geographical and bathymetrical distribution range information involving new records for the Atlantic (e.g., Montano et al. 2017a; Van der Loos and Prud’homme van Reine 2017).The present special issue of Marine Biodiversity on Caribbean coral reefs serves to add information on these points

Dutch below

Coralita is an ornamental plant that was introduced to several Caribbean islands but has quickly found its way to the top of the invasive species lists for the Dutch Caribbean.  Its fast-growing vines smother and outcompetes native vegetation, changing the landscape of the islands. Conservations efforts include manual removal, herbicides and awareness campaigns. 

Coralita vine flowering. Photo credit: Marjolijn Lopes Cardozo

It is easy to fall in love with coralita. This ornamental plant, also known as the coral vine (Antigonon leptopus) was introduced to a number of Caribbean islands as a garden accessory in the 1940s.  Its brightly colored flowers and quickly growing vines make quite the statement piece in any garden. In its native territory, growth of this plant is limited by droughts, however in the Dutch Caribbean this plant has been flourishing. Within the Dutch Caribbean, coralita has been able to spread quickly, year round, due to it’s ability to grow near water collection points such as drainage channels. 

Consequences 

Coralita can spread very quickly. Its vines can reach up to 15 meters in length and rapidly cover entire areas of land. This vine is able spread both horizontally (across fields) or vertically (up trees and buildings), smothering native vegetation beneath it. In addition, this decrease in native flora is also impacting local insect and spider communities.  In fact, researchers from the Vrije Universiteit Amsterdam were able to demonstrate that on St. Eustatius, in areas of dense coralita, there was a decrease in native insects and spiders. Although often thought of as pests, these creatures play a critical role in the local ecosystem by serving as pollinators, aiding in decomposition and nutrient cycling as well as serving as a food source for native reptiles and birds.  Decrease in native vegetation and thus a decrease in insects and spiders will have a cascading effect in limiting the biodiversity of these islands in the future. 

Coralita smothering local vegetation. Photo credit: Achsah Mitchell

Innovative Ideas 

Luckily, islands have some creative ways of combating this issue. In 2018, individuals from the St. John’s community on Saba planted five lemon trees to bring attention to and work towards the eradication of the invasive vine.  Land was selected and cleared, to be used as a fruit orchard, both working to eliminate coralita and provide a source of fresh fruit for the island. Overall, this project served to encourage community action (planting lemon trees) to achieve a common goal (removing coralita). 

On St. Eustatius, researchers have found a novel way to use a classification map to help managers quickly identify dense areas of coralita.  In fact, using this method, they showed that coralita is not randomly spread across the island, but typically found along roads and drainage channels.  Overall, the vine was found more commonly in grasslands, disturbed natural areas and urban sites and rarely in undisturbed natural forest. This information will be key in constructing an invasive species management for the island.

Future work 

Photo credit: Jasper Molleman

The impact of coralita on the Dutch Caribbean is significant. It not only threatens the biodiversity of the islands, but it also has economic consequences, such as reduced tourism appeal and increased costs of removal efforts. Education is an important first step to getting involved in local conservation efforts. Current efforts include manual removal by trained volunteers and the use of herbicides to control the plant’s growth. In addition, awareness campaigns are being conducted to educate residents and visitors on the importance of protecting native vegetation and preventing the spread of invasive species.  

DCNA  

The Dutch Caribbean Nature Alliance (DCNA) supports science communication and outreach in the Dutch Caribbean region by making nature related scientific information more widely available through amongst others the Dutch Caribbean Biodiversity Database, DCNA’s news platform BioNews and through the press. This article is part of a series of articles on ‘Invasive Alien Species in the Dutch Caribbean”. This article contains the results from several scientific studies but the studies themselves are not DCNA studies. No rights can be derived from the content. DCNA is not liable for the content and the in(direct) impacts resulting from publishing this article.   

Coralita is een sierplant die op verschillende Caribische eilanden is geïntroduceerd, maar al snel zijn weg naar de top van de invasieve soortenlijsten voor de Nederlandse Cariben heeft gevonden. De snelgroeiende ranken verstikken en verdringen de inheemse vegetatie, waardoor het landschap van de eilanden verandert. Instandhoudingsinspanningen omvatten handmatige verwijdering, herbiciden en bewustmakingscampagnes.

Invasieve Coralita. Foto: Marjolijn Lopes Cardozo

Het is gemakkelijk om verliefd te worden op coralita. Deze sierplant, ook wel bekend als de koraalklimmer (Antigonon leptopus), werd in de jaren 40 op een aantal Caribische eilanden geïntroduceerd als tuinaccessoire. De felgekleurde bloemen en snelgroeiende ranken zijn een blikvanger in elke tuin. In zijn inheemse grondgebied wordt de groei van deze plant beperkt door droogtes, maar in de Nederlandse Cariben woekert deze plant. Binnen het Nederlandse Caribisch gebied kan coralita zich het hele jaar door snel verspreiden omdat het in de buurt van waterverzameling, zoals drainagekanalen, groeit.

Gevolgen

Coralita kan zich zeer snel verspreiden. De ranken kunnen tot 15 meter lang worden en bedekken snel hele stukken land. Deze rank kan zich zowel horizontaal (over velden) als verticaal (op bomen en gebouwen) verspreiden en de inheemse vegetatie eronder verstikken. Bovendien heeft deze afname van de inheemse flora ook gevolgen voor lokale insecten en spinnen. Onderzoekers van de Vrije Universiteit Amsterdam konden zelfs aantonen dat er op St. Eustatius, in gebieden met veel coralita, een afname was van inheemse insecten en spinnen. Hoewel ze vaak als ongedierte worden beschouwd, spelen deze wezens een cruciale rol in het lokale ecosysteem door als bestuivers te dienen, te helpen bij de afbraak en de kringloop van voedingsstoffen en als voedselbron voor inheemse reptielen en vogels. Afname van inheemse vegetatie en dus afname van insecten en spinnen zal een cascade-effect hebben bij het beperken van de biodiversiteit van deze eilanden in de toekomst.

Invasieve Coralita. Foto: Achsah Mitchell

Innovatieve ideeën

Gelukkig hebben eilanden een aantal creatieve manieren om dit probleem te bestrijden. In 2018 hebben individuen uit de St. John’s-gemeenschap op Saba vijf citroenbomen geplant om aandacht te vragen voor en te werken aan de uitroeiing van de invasieve coralita. Er werd land geselecteerd en gekapt om te worden gebruikt als fruitboomgaard, zowel om coralita te elimineren als om een bron van vers fruit voor het eiland te bieden. Over het algemeen diende dit project om gemeenschapsactie aan te moedigen (citroenbomen planten) om een gemeenschappelijk doel te bereiken (coralita verwijderen).

Op St. Eustatius hebben onderzoekers een nieuwe manier gevonden om een classificatiekaart te gebruiken om managers te helpen snel gebieden met veel coralita te identificeren. Met deze methode toonden ze zelfs aan dat coralita niet willekeurig over het eiland wordt verspreid, maar meestal langs wegen en afwateringskanalen wordt aangetroffen. Over het algemeen werd de rank vaker aangetroffen in graslanden, verstoorde natuurgebieden en stedelijke gebieden en zelden in ongestoord natuurlijk bos. Deze informatie zal van cruciaal belang zijn bij het opzetten van een beheer van invasieve soorten voor het eiland.

Toekomstwerk

Foto: Jasper Molleman

Het effect van coralita op Caribisch Nederland is aanzienlijk. Het bedreigt niet alleen de biodiversiteit van de eilanden, maar heeft ook economische gevolgen, zoals verminderde aantrekkingskracht voor het toerisme en hogere kosten voor verwijderingsinspanningen. Onderwijs is een belangrijke eerste stap om betrokken te raken bij lokale inspanningen voor natuurbehoud. Huidige inspanningen omvatten handmatige verwijdering door getrainde vrijwilligers en het gebruik van herbiciden om de groei van de plant te beheersen. Daarnaast worden bewustmakingscampagnes gevoerd om bewoners en bezoekers voor te lichten over het belang van het beschermen van inheemse vegetatie en het voorkomen van de verspreiding van invasieve soorten.

DCNA

De Dutch Caribbean Nature Alliance (DCNA) ondersteunt wetenschapscommunicatie en outreach in de Nederlandse Caribische regio door natuurgerelateerde wetenschappelijke informatie breder beschikbaar te maken via onder meer de Dutch Caribbean Biodiversity Database, DCNA’s nieuwsplatform BioNews en via de pers. Dit artikel maakt deel uit van een serie artikelen over ‘Invasive Alien Species in the Dutch Caribbean’. Dit artikel bevat de resultaten van verschillende wetenschappelijke onderzoeken, maar de onderzoeken zelf zijn geen DCNA-onderzoeken. Aan de inhoud kunnen geen rechten worden ontleend. DCNA is niet aansprakelijk voor de inhoud en de indirecte gevolgen die voortvloeien uit het publiceren van dit artikel.

Published in BioNews 63

Abstract

1.  Biodiversity inventories and monitoring techniques for marine fishes often over-look small (<5  cm), bottom-associated (‘cryptobenthic’) fishes, and few stand-ardized, comparative assessments of cryptobenthic fish communities exist. We sought to develop a standardized, quantitative survey method for cryptobenthic fishes that permits their sampling across a variety of habitats and conditions.

2.  Fish-   specific autonomous reef monitoring structures (FARMS) are designed to sample cryptobenthic fishes using a suite of accessible and affordable materials. To generate a variety of microhabitats, FARMS consist of three layers of stacked PVC pipes in three different sizes, as well as a bottom and top level of loose PVC pipe fragments in a mesh basket. We deployed FARMS across a variety of habitats, including coral reefs, seagrass beds, oyster reefs, mangroves, and soft- bottom habitats across six locations (Hawai'i, Texas, Panama, Saudi Arabia, Brazil, and Curaçao).

3.  From shallow estuaries to coral reefs beyond 100 m depth, FARMS attracted distinct communities of native cryptobenthic fishes with strong site or habitat speci ficity. Comparing the FARMS to communities sampled with alternative methods (enclosed clove-oil stations on coral reefs in Panama and oyster sampling units on oyster reefs in Texas) suggests that FARMS yield a subset of cryptobenthic fishspecies that are representative of those present on local coral and oyster reefs. While FARMS yield fewer individuals per sample, they are efficient sampling de-vices relative to the sampled area.

4.  We demonstrate that FARMS represent a useful tool for standardized collections of cryptobenthic fishes. While natural substrata are bound to yield more mature communities with a larger number of individuals and wider range of specialist spe-cies, the potential to deploy and retrieve FARMS in turbid environments, beyond regular SCUBA depth, and where fish collections using anaesthetics or ichthyo-cides are forbidden suggests that they are a valuable complementary technique to survey fishes in aquatic ecosystems. Deploying FARMS in locations and habi-tats where cryptobenthic fish communities have not been studied in detail may yield many valuable specimens of unknown or poorly known species.KEYWORDSartificial habitat, biodiversity, biogeography, coral reef fishes, fish trap, fisheries-independent sampling, taxonomic inventory

Abstract
Since the severe decline of the Acropora populations in Bonaire in the 1980s, no assessment has characterized the distribution of remnant colonies. Because of their patchy distribution, a large sampling effort is necessary to adequately describe their occurrence. However, the spatial scale at which this assessment needs to be carried out makes this prohibitive with approaches such as transects using SCUBA gear and photogrammetry. This internship project aimed to optimize and apply a simple methodology trialed by relevant stakeholders on the island to obtain coarse but spatially explicit data with relatively low time-investment. Snorkelers utilizing a waterproof GPS and a slate to record coarse categorical data outlined patches of Acropora cervicornis and Acropora palmata in-situ. These were processed with an ArcGIS workflow to create shapefiles of coral patches as polygons joined to their corresponding data. The resulting polygons were used to describe the distribution of Acropora spp. along the leeward coast of Bonaire. Furthermore, these were used as ground-truthing data to test whether remote sensing imagery can be used to detect A. cervicornis remotely. 466 polygons along 14.5km of the coast were created, showing a patchy distribution of both species, more frequent occurrence of A. palmata in the northern leeward coast compared to the southern, and vice-versa for A. cervicornis. A multinomial logistic regression, maximum likelihood classification, and forest-based classification all showed a high accuracy in labelling A. cervicornis correctly in remote sensing data, but all showed frequent misclassification of other reef structures as A. cervicornis. The mapping approach presented in this internship could be applied to investigate fragmentation effects in Acropora populations and to gather in-situ ground-truthing data for other benthic habitats.

For full report or more information,  please contact erik.meesters@wur.nl or gulsah.dogruer@wur.nl

Notes from a series of sessions to jointly define a biodiversity monitoring strategy. The sessions were organized by the Dutch Caribben Nature Alliance (DCNA) and Rijksdienst Caribisch Nederland (RCN). Nature parks from Aruba (ARIKOK), Bonaire (STINAPA), Curacao (CARMABI), St.Maarten (Nature Foundation St.Maarten), Saba (Saba Conservation Foundation) and St.Eustatius (STENAPA) contributed to the sessions.

Nederlands Below

Land and freshwater mollusks were surveyed over the course of three visits in 2015, 2020 and 2021 on the Dutch and French sides of St. Maarten. Snails are important for a healthy soil and are an important food source for many species. Alarmingly, it has become clear that a number of land snail species are declining. In fact, it is suspected that a number of species will disappear completely if no action is taken soon.

Rare and/or endangered snails

Striped Helicinid (Helicina fasciata)- Photo credit: Tello Neckheim

About 49 species of mollusks (namely clams and snails) have been documented on St. Maarten. Depending on which list you use, between 15 and 16 of which are endangered, representing about a third of the island’s mollusk populations. Unfortunately, too little research has been done on these mollusks to make definitive conclusions, but it appears that four species may have already been lost, including the Apple Snail (Pomacea glauca), Marbled Physa (Aplexa marmorata), Glabrous Ramshorn (Biomphalaria glabatra) and Mottled Fingernail Clam (Eupera viridans).  And the terrestrial snails Pupiform Mountain Snail (Chondropoma pupiforme), Striped Helicinid (Helicina fasciata), Transparant Bulimulus (Bulimulus diaphanous fraterculus) and some more species are endangered on St. Maarten.

Critical Habitats

Pleurodonte guadeloupensis martinensis- Photo credit: Tello Neckheim

The main causes of the decline in populations include habitat loss due to hurricanes, pollution and construction. In fact, the island has almost no primary (or original) forest left. Secondary forest is restored forest where, in addition to indigenous species of plants and animals, there are often many introduced exotic species which can bring about a number of other issues for the island.

One particularly vulnerable habitat is forest with calcareous moist soil. On the Dutch side of the island, this habitat is mainly found at Billy Folly, where only a limited piece of original habitat is still present. Nearly the entire “mountain” has now been built up with houses. During the 2021 visit, a road was built right through the primary forest. This road will likely lead to new construction projects, which could result in the disappearance of the last remnant of forest causing the loss of any snail species bound to this area.

Another disappearing habitat is moist secondary forest on neutral soil. This habitat is mainly found on the French part around Mont Paradis. This habitat is scarce but not threatened because there are no building plans on and around Mont Paradis. On the Dutch side it is found on Sentry hill and Sint Peter hill.

Importance of snails

These snails represent an important part of the natural balance for the island.  They consume rotting leaf litter and fungi and can help recycle nutrients in the soil.  In addition, they provide food source to a number of mammals, birds, reptiles and even insects, helping convert nutrients found in the soil to a digestible food source for larger predators.  A healthy environment for St. Martin starts in the soil, so understanding and preserving these tiny island inhabitants will be critical in protecting the island’s delicate ecological balance.

Report your sightings

Have you observed snails? Report your nature sightings and photos on the website www.Observation.org or download the free apps (iPhone (iObs) & Android (ObsMapp)).

Species reports by local communities and tourists are invaluable for nature conservation efforts to help increase public awareness and overall species protection. Besides, DCNA, Observation International and Naturalis Biodiversity Center are working together to develop on automated species identification app for your phone. Your uploaded photos are of great value to make this possible. For questions, please contact research@DCNAnature.org

Read more

You can find the completed list of land and freshwater mollusks documented during this study on the Dutch Caribbean Biodiversity Database.

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Verdwijnen van slakken op Sint Maarten

Land- en zoetwaterweekdieren zijn onderzocht tijdens drie bezoeken in 2015, 2020 en 2021 op de Nederlandse en Franse kant van St. Maarten. Slakken zijn belangrijk voor een gezonde bodem en zijn een belangrijke voedselbron voor veel soorten. Verontrustend is de bevinding dat een aantal soorten landslakken achteruitgaat. Sterker nog, het vermoeden bestaat dat een aantal soorten volledig zal verdwijnen als er niet snel actie wordt ondernomen.

Zeldzame en/of bedreigde slakken

Striped Helicinid (Helicina fasciata)- Photo credit: Tello Neckheim

Ongeveer 49 soorten weekdieren (kokkels en slakken) zijn gedocumenteerd op St. Maarten. Afhankelijk van de lijst die gebruikt wordt, zijn er tussen de 15 en 16 bedreigd, die ongeveer een derde van de weekdierpopulaties van het eiland vertegenwoordigen. Helaas is er te weinig onderzoek gedaan naar deze weekdieren om definitieve conclusies te trekken, maar het lijkt erop dat er al vier soorten verloren zijn gegaan, waaronder de Appelslak (Pomacea glauca), Gemarmerde Physa (Aplexa marmorata), Glabrous Ramshorn (Biomfalaria glabatra) en Mottled Fingernail Clam (Eupera viridans). En de landslakken Pupiform Mountain Snail (Chondropoma pupiforme), Striped Helicinid (Helicina fasciata), Transparante Bulimulus (Bulimulus diaphanous fraterculus) en nog enkele andere soorten worden bedreigd op St. Maarten.

Kritieke Habitats

Pleurodonte guadeloupensis martinensis- Photo credit: Tello Neckheim

De belangrijkste oorzaken van de achteruitgang van de populaties zijn het verlies van leefgebieden als gevolg van orkanen, vervuiling en constructie. In feite heeft het Franse deel van het eiland bijna geen primair (of origineel) bos meer. Secundair bos is hersteld bos waar, naast inheemse soorten planten en dieren, vaak veel geïntroduceerde exotische soorten zijn die een aantal andere problemen voor het eiland veroorzaken.

Een bijzonder kwetsbare habitat is bos met kalkrijke vochtige grond. Aan de Nederlandse kant van het eiland is dit leefgebied vooral te vinden bij Billy Folly, waar nog maar een beperkt stukje oorspronkelijk leefgebied aanwezig is. Bijna de hele “berg” is nu bebouwd met huizen. Tijdens het bezoek van 2021 is er een weg aangelegd dwars door het oerbos. Deze weg zal waarschijnlijk leiden tot nieuwbouwprojecten, wat kan leiden tot het verdwijnen van het laatste restant van het bos, waardoor alle aan dit gebied gebonden slakkensoorten verloren gaan.

Een ander verdwijnend leefgebied is vochtig secundair bos op neutrale grond. Dit leefgebied komt vooral voor op het Franse deel rond Mont Paradis. Dit leefgebied is schaars maar niet bedreigd omdat er geen bouwplannen zijn op en rond Mont Paradis. Aan de Nederlandse kant is het te vinden op Sentry hill en Sint Peter hill.

Belang van slakken

De slakken vormen een belangrijk onderdeel van het natuurlijke evenwicht van het eiland. Ze consumeren rottend bladafval en schimmels en kunnen helpen voedingsstoffen in de bodem te recyclen. Bovendien vormen ze een voedselbron voor een aantal zoogdieren, vogels, reptielen en zelfs insecten, en helpen ze voedingsstoffen in de bodem om te zetten in een verteerbare voedselbron voor grotere roofdieren. Een gezonde omgeving voor St. Maarten begint in de bodem, dus het begrijpen en behouden van deze kleine eilandbewoners zal van cruciaal belang zijn bij het beschermen van het delicate ecologische evenwicht van het eiland.

Meld je natuur waarnemingen

Heb je slakken gezien? Meld dan je natuurwaarnemingen en foto’s op de website www.Observation.org of download de gratis apps (iPhone (iObs) & Android (ObsMapp)).

Soortenrapporten door lokale gemeenschappen en toeristen zijn van onschatbare waarde voor inspanningen op het gebied van natuurbehoud om het publieke bewustzijn en de algemene bescherming van soorten te vergroten. Daarnaast werken de Dutch Caribbean Nature Alliance (DCNA), Observation International en Naturalis Biodiversity Center samen aan de ontwikkeling van een app voor je telefoon voor het geautomatiseerd identificeren van soorten. Uw geüploade foto’s zijn van grote waarde om dit mogelijk te maken. Neem voor vragen contact op met research@DCNAnature.org

Meer informatie

De volledige lijst van land- en zoetwaterweekdieren die tijdens dit onderzoek zijn gedocumenteerd, vindt u in de Dutch Caribbean Biodiversity Database.

Published in BioNews 52

Abstract The Bonaire Marine Biodiversity Expedition (2019) was organized by Naturalis Biodiversity Center in Leiden (the national museum of natural history of the Netherlands), ANEMOON Foundation (a Dutch organisation of marine ecological research involving citizen science), and STINAPA Bonaire National Parks Foundation. This field survey explored the marine biota of Bonaire, an island in the southern Caribbean. Species lists were produced of several groups of organisms, which include many new records for Bonaire and also some species new for science

In exciting news for the Bonaire National Marine Park (BNMP), a sighting of Aegires sublaevis, a rare nudibranch, was documented at the Cliff dive site in 2021. Incredibly, this nudibranch has not been documented anywhere in the Caribbean, and this extraordinary discovery showcases the diversity – known and unknown – of the reefs protected in the BNMP since 1979. Bonaire continues to win scuba-diving awards worldwide for its beautiful macro-life and this discovery only further highlights why reef conservation is vitally important.  

Nudibranchs, a type of mollusk, fascinate both biologists and scuba-divers world-wide. A diverse group, members are known for their elaborate colors, ability to photosynthesize, and sometimes cannibalistic behaviors, gaining them a passionate following from both underwater photographers and scientists alike. Forums around the world unite researchers, scientists, and photographers in their quest to discover and document these tiny creatures with big personalities. It is through one such forum that researcher Dr. Leslie Wilk, co-author of Reef Creature Identification: Florida Caribbean Bahamas, tracked down author Tricia O’Malley, an amateur underwater photographer, as she had the only known photographs in the Caribbean of the rare nudibranch, Aegires sublaevis.  

Rare nudibranch Aegires sublaevis. Photo source: Tricia O’Malley

“I affectionately referred to the nudibranch as “Glow Cheese,” because I was unable to find the correct identification. Its brilliant yellow color and patchy skin made me think of a block of Swiss Cheese. I was delighted to discover it at the Cliff dive site – one of my favorite locations for macro life and night diving,” O’Malley states.  

Incidentally, through discussion with Dr. Wilk, O’Malley learned that she’d also documented another rare nudibranch at the same site – an undescribed member of the family Dorididae.  

“I take joy in night diving because the reefs truly come alive in the dark. It is astounding to me that after hundreds of dives at Bonaire, I still discover new and exciting finds on each dive. The Cliff dive site is particularly bountiful when it comes to finding nudibranchs, and I can’t tell you how excited I am to have had the opportunity to see such rare and unusual macro-life. I’m truly honored to live somewhere that declares their commitment to protecting the reefs. It just shows that there is so much more to learn about the delicate reef ecosystem and that the Netherlands should consider Bonaire’s reef to be a crown jewel to be preserved at all costs,” O’Malley continues. 

Unidentified Doridae. Photo source: Tricia O’Malley

In his research, Dr. Wilk also discovered other rare nudibranchs found on Bonaire by local naturalist, Ellen Muller. These nudibranchs are Trapania bonellenae, as well as an undescribed species of Cerberilla. These finds only serve to further highlight the extraordinary diversity of Bonaire’s reef.  

“Recent finds show that Bonaire, in particular, has several rare and undescribed species.  The rarest is Trapania bonellenae, an endemic slug named partly after the island and partly after the local resident who discovered it. Aegires sublaevis, a species rarely seen anywhere, was recently photographed at Bonaire. Undescribed species of Spurilla, Cerberilla, and Dorididae have been found in Bonaire’s shallows, but nowhere else. There is also a rare color form of Elysia flava,” Dr. Wilk states.  

Unknown Doridae. Photo source: Tricia O’Malley

“Such extraordinary aspects of Bonaire’s sea slug fauna extend to other marine taxa. For example, the preliminary results of a 2020 survey of Bonaire’s marine biodiversity, funded by Naturalis Biodiversity Center and the ANEMOON Foundation, discovered the existence of at least seven species of invertebrates that are new to science. I mention the above to highlight that on-going research is revealing Bonaire’s marine life to be more diverse and remarkable than ever expected. Accordingly, governmental authorities that create and implement Bonaire’s coastal development policies should place even more emphasis on making decisions that respect, protect, and preserve its marine environment,” Dr. Wilk states. 

Implications 

These findings provide exciting new insight into Bonaire’s coral reef ecosystems and the opportunity for new marine life discoveries. It is vitally important to protect an environment where new species are still being discovered. As development on Bonaire increases, so does the pressure on the dynamic reef ecosystem, and it will be crucial that conservation lead Bonaire’s future. 

The discovery of the Aegires sublaevis will be published in the upcoming field guide “Tropical West Atlantic Sea Slugs.” 

Report your sightings 

These nudibranch sightings have been stored in Observation.org: https://observation.org/observation/229037868/ 

Species reports by local communities and tourists are invaluable for nature conservation efforts to help increase public awareness and overall species protection.  

You can report your nature sightings and photos on the website www.Observation.org or download the free apps (iPhone (iObs) & Android (ObsMapp)). You can also send your information to research@DCNAnature.org for support with getting your data stored. 

Article published in BioNews 50.

Researchers from University of Amsterdam and CARMBABI Foundation implemented 3-dimensional reef surveying techniques to improve representation of species found within hidden cavities previously overlooked by 2D methods. 12 sites along the coast of Curacao were selected and analyzed. Improved surveying techniques will increase overall understanding of the complexities of these vital ecosystems.

Photo Source: Niklas Kornder

Coral reefs are one of the most diverse ecosystems on the planet.  Coral’s beautiful skeletal structure plays an important role in providing reef habitat, nursery and hunting ground while also protecting coastal zones.  Climate change continues to be a significant threat to these areas, making the need for accurate mapping and surveying techniques vital to researchers’ ability to detect change. Traditional mapping techniques use a 2D approach to project surface cover estimates throughout a 3D structure.  Unfortunately, this technique misses hidden habitats, such as overhangs and cavities, which can result in an under representation of biomass estimates.

Photo Source: Eric Mijts

2D versus 3D

New research from the University of Amsterdam and CARMBABI Foundation compared 2D versus 3D survey techniques. Traditionally, organism abundance was calculated as the percentage of projected reef cover.  Previously, this was done by 2D surveys, however a new strategy hopes to improve on this technique through the combination of photograph analysis, diving surveys and computer modeling. Researchers surveyed 12 coral areas on the island of Curacao, then compared 3D benthic community estimates against traditional 2D projected surface cover analysis.

The Results

During this research, scientists found that while using 2D techniques, the relative contribution of organisms which grow vertically (gorgonians and massive sponges) was up to two times and 11 times lower, respectfully, than their contribution to reef biomass.  In addition, hidden areas represented nearly half of all total reef substrate, meaning two thirds of all coralline algae and almost all encrusting sponges are not included within traditional surveying techniques.

Using a variety of different metrics, this research presents adjustments to current monitoring techniques, highlighting the importance of evaluating the ecological contributions of previously disregarded or underrepresented species.  These metric conversions can be used to complement traditional survey techniques to provide improved estimates for biovolume, biomass and element composition (stocks of organic carbon and nitrogen) within coral reef communities.

Implications

Photo source: Francesco Ungar

Understanding the true composition of coral reefs is vital for designing and implementing effective conservation strategies. Coral’s unique ability to create complex habitats is vital to maintaining high community diversity and abundance in shallow water environments.  It is estimated that nearly 75-90% of coral reef ecosystems are hidden under the surface skeleton.  This means that for every m2 that can be seen, there is up to 8m2 of additional habitat underneath. This study suggests that 2D approaches may be useful to produce relatively fast estimates of reef ‘health’ but a 3D approach is needed to understand coral reef’s true composition.

https://www.dcbd.nl/document/implications-2d-versus-3d-surveys-measure-a...

Article published in BioNews 47