Invasive seagrass

Invasive seagrass and native upside-down jellyfish are battling for space

Dutch, Papiamentu, and Papiamento below

Researchers from Wageningen University & Research and the University of Amsterdam report on a fascinating case of competition between an animal and an invasive plant. In tropical ecosystems, photosynthesizing organisms are continuously competing for space and light. The invasive seagrass Halophila stipulacea has been very successful in new habitats both in the Mediterranean and Caribbean seas. 

Photo: Erik Wurz

The seagrass can quickly colonize new habitats because small fragments break off, remain viable and spread via currents. In the new paper Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass published in the scientific journal Ecology, the researchers report on their discovery that the invasive seagrass uses little mounds – created by burrowing animals as shrimp or seacucumbers – as a new habitat to settle and expand from. The mounds provide new space with sufficient light, opening up the dense meadows of native seagrass where the invasive seagrass otherwise cannot settle. From there, they observed that the invasive seagrass can spread. 

High and open locations are in demand 

Researching the habitat of the upside-down jellyfish (Source: Erik Wurz)  Photo: Erik Wurz

But the researchers also found that this can cause problems for native species. “The upside-down jellyfish (Cassiopea spp) lies upside down because it has photosynthetic algae in its tentacles. Therefore, these organisms also need light and prefer open spaces such as these mounds created by burrowing animals,” according Fee Smulders of Wageningen University & Research, and lead author of the study. “Msc student Naomi Slikboer recorded the presence of both invasive seagrass and upside-down jellyfish on many of these mounds on the island of Curaçao. She found that often the invasive seagrass pushes the upside-down jellyfish out of these habitats over time.” 

 

Jellyfish move away more often 

Researching the habitat of the upside-down jellyfish (Source: Erik Wurz) Photo: Erik Wurz

This probably increases the energetic costs for the jellyfish as it has to move more often due to rapid overgrowth of H. stipulacea. Additionally, the authors hypothesize that the interplay between invasive seagrass and burrowing mounds will lead unstable, dynamic seagrass meadows, unfavorable for valuable native seagrass species. Smulders: “We need to keep a close watch on this invasive seagrass and investigate the impact on both native species as well as the seascape patch dynamics in Caribbean seagrass meadows.” 

For more information fin the article Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass  published in the scientific journal Ecology in the DCBD database. 

The 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 contains the results of one of those scientific studies but the study itself is not a DCNA study. 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. 

Text: Wageningen Environmental Research

 

 

Onderzoekers van Wageningen University & Research en de Universiteit van Amsterdam hebben ontdekt dat een invasieve plant de competitie aangaat met een inheemse kwal. De zeegrassoort Halophila stipulacea is erg succesvol in het koloniseren van nieuwe gebieden in de Middellandse Zee en de Cariben. 

Onderzoek naar leefgebied inheemse ‘ondersteboven’ kwal in het Caribisch gebied (Bron: Erik Wurz)

Het zeegras kan zich verspreiden doordat fragmentjes afbreken, lang in leven blijven en met de stroming mee nieuwe gebieden bereiken. In het nieuwe artikel Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass in het wetenschappelijke tijdschrift Ecology beschrijven de onderzoekers hun ontdekking dat het invasieve zeegras kleine heuveltjes – gemaakt door gravende diertjes als garnalen of zeekomkommers – gebruikt als startpunt om nieuwe gebieden te begroeien. Deze heuveltjes bieden ruimte en licht, een ideale omgeving voor het zeegras. Vanaf daar kan de invasieve plant zich verspreiden door het inheemse grasveld. 

Lichte, hoge plekken zijn gewild 

Onderzoek naar leefgebied inheemse ‘ondersteboven’ kwal in het Caribisch gebied (Bron: Erik Wurz)

Maar de onderzoekers ontdekten ook dat dit problemen op kan leveren voor inheemse soorten. “De ‘ondersteboven’ kwal (Cassiopea spp) ligt op zijn rug omdat er fotosynthetiserende algen in zijn tentakels zitten. Daarom hebben deze kwallen ook licht nodig, en verblijven ze graag op open plekken zoals de kale heuveltjes,” zegt Fee Smulders, promovendus bij Wageningen University & Research en hoofdauteur van de studie. “MSc student Naomi Slikboer volgde een aantal van deze heuvels door de tijd, en noteerde de aanwezigheid van zowel de kwallen als het invasieve zeegras op Curaçao. Zij ontdekte dat er in het begin veel kwalletjes op de heuvels lagen, maar dat de meeste heuvels op het eind begroeid waren met invasief zeegras.” 

 

Kwallen verhuizen vaker 

Onderzoek naar leefgebied inheemse ‘ondersteboven’ kwal in het Caribisch gebied (Bron: Erik Wurz)

Door de komst van het zeegras moeten de kwallen vaker verhuizen en verliezen ze mogelijk hun habitat. Verder verwachten de onderzoekers dat het samenspel tussen het invasieve zeegras en de heuveltjes zal zorgen voor een onstabiel dynamisch zeegrasveld, wat nadelig is voor het waardevolle inheemse zeegras. Smulders: “Het is belangrijk om deze exoot goed in de gaten te houden en zijn invloed op zowel inheemse soorten als het gehele onderwaterlandschap te onderzoeken.” 

Meer informatie 

Het artikel Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass in het wetenschappelijke tijdschrift Ecology. 

Tekst: Wageningen Environmental Research
 

DCNA 

De Dutch Caribbean Nature Alliance (DCNA) ondersteunt wetenschapscommunicatie en outreach in het Nederlandse Caribisch gebied door natuurgerelateerde wetenschappelijke informatie breder beschikbaar te maken via onder andere de Dutch Caribbean Biodiversity Database, DCNA’s nieuwsplatform BioNews en via de pers. Dit artikel bevat de resultaten van een van die wetenschappelijke onderzoeken, maar het onderzoek zelf is geen DCNA-onderzoek. Aan de inhoud kunnen geen rechten worden ontleend. De DCNA is niet aansprakelijk voor de inhoud en de indirecte gevolgen die voortvloeien uit het publiceren van dit artikel. 

 

 

Investigadónan di Wageningen Unisversity & Research i Universidat di Amsterdam a deskubrí un mata invasivo ku ta kompetí ku un kimakima indígeno. E espesie di yerba di laman Halophila stipulacea ta hopi eksitoso den kolonisashon di áreanan nobo den Laman Mediteráneo i den Karibe.

Investigashon pa loke ta trata e área di biba di e kimakima indígena ‘ariba abou’ den área karibense (Fuente: Erik Wurz)

E yerba di laman por plama pa motibu ku hopi fragmento chikitu ta kibra kita ‘fo, keda na bida hopi tempu largu i alkansá áreanan nobo pa medio di drif bai ku koriente di laman. Den e artíkulo nobo ‘ Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass’ den e revista sientífiko Ecology, e investigadónan ta deskribí kon nan a deskubrí ku e yerba di laman invasivo ta usa seritu chikitu – ku bestia ku ta koba manera kabaron òf lol’i awa ta traha – komo punto di salida pa krese den áreanan nobo. E seritunan akí ta ofresé espasio i klaridat, un ambiente ideal pa e yerba di laman. For di einan e mata invasivo por plama atraves di e kama di yerba di laman. 

Sitionan haltu ku klaridat ta hopi gustá 

Investigashon pa loke ta trata e área di biba di e kimakima indígena ‘ariba abou’ den área karibense (Fuente: Erik Wurz)

Pero e investigadónan a deskubrí ku esaki por okashoná problemá tambe pa espesienan indígeno. “E kimakima ‘ariba abou’ (Cassiopea spp) ta drumi riba su lomba, pasobra tin alga fotosintétiko den su tenglanan. P’esei e kimakimanan akí tin mester di klaridat tambe, i nan gusta permanesé na sitionan habrí, manera e seritunan sin nada riba nan”, segun Fee Smulders, ku ta serka di optené su título komo dòktor na Wageningen University & Research i kende ta e outor prinsipal di e investigashon akí. “Durante algun tempu e studiante pa Master of Science Naomi Slikboer a sigui e seritunan akí, i el a nota presensia di tantu e kimakimanan komo e yerba di laman invasivo na Kòrsou. El a deskubrí ku na kuminsamentu tabatin hopi kimakima riba e seritunan, pero ku na final mayoria di e seritunan tabatin yerba di laman invasivo ta krese riba nan.” 

 

Kimakima ta muda mas biaha 

Investigashon pa loke ta trata e área di biba di e kimakima indígena ‘ariba abou’ den área karibense (Fuente: Erik Wurz)

Pa motibu di binida di e yerba di laman, e kimakimanan mester muda mas biaha i posibelmente nan ta pèrdè nan habitat. Mas aleu e investigadónan ta verwagt ku e interakshon entre e yerba di laman invasivo i e seritunan lo sòru pa un kama di yerba di laman dinámiko i instabil, loke ta desbentahoso pa e yerba di laman indígeno balioso. Smulders: “Ta importante pa vigilá e espesie eksótiko akí bon i investigá su influensia riba tantu e espesienan indígeno komo riba henter e paisahe bou di laman.” 

Mas informashon 

E artíkulo ‘ Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass’ den e revista sientífiko Ecology. 

 

Teksto: Wageningen Environmental Research 

 

 DCNA 

Duthc Caribbean Nature Allianc (DCNA) ta sostené komunikashon sientífiko i alkanse den región hulandes karibense pa medio di hasi informashon sientífiko relatá na naturalesa disponibel den un forma mas amplio, via entre otro Dutch Caribbean Biodiversity Database, e plataforma di notisia BioNews di DCNA i via prensa. E artíkulo akí ta kontené resultado di un di e investigashonnan sientífiko ei, pero e investigashon mes no ta un investigashon di DCNA. No por derivá ningun derecho for di e kontenido. DCNA no ta responsabel pa e kontenido i e konsekuensianan (in)direkto ku ta surgi  pa motibu di publikashon di e artíkulo akí.  

 

 

Investigadonan di Wageningen University & Research y Universidad di Amsterdam a descubri un mata invasivo cu ta competi cu un kimakima indigeno. E especie di yerba di lama Halophila stipulacea ta hopi exitoso den colonisacion di area nobo den Lama Mediteraneo y den Caribe.

Investigacion pa loke ta trata e area di biba di e kimakima indigena “ariba abou” den area Caribense (Fuente: Erik Wurz)

E yerba di lama por plama pa motibo cu hopi fragmento chikito ta kibra kit’afo, ta keda na bida hopi tempo largo y ta alcansa area nobo door di drif bay cu coriente di lama. Den e articulo nobo Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass den e revista cientifico Ecology, e investigadonan ta describi con nan a descubri cu e yerba di lama invasivo ta uza serito chikito – traha door di bestia cu ta coba manera cabaron of lol’i awa – como punto di salida pa crece den area nobo. E seritonan aki ta ofrece espacio y claridad, un ambiente ideal pa yerba di lama. For di eynan e mata invasivo por plama atraves di e cama di yerba di lama.

Sitio halto cu claridad ta hopi gusta

Researching the habitat of the upside-down jellyfish (Source: Erik Wurz)  Photo: Erik Wurz

Pero e investigadonan a descubri cu esaki por ocasiona problema tambe pa especienan indigeno. “E kimakima ‘ariba abou’ (Cassiopea spp) ta drumi riba su lomba, pasobra tin alga fotosintetico den su tenglanan. P’esey e kimakimanan aki mester di claridad tambe, y nan gusta permanece na sitio habri, manera e seritonan sin nada riba nan”, segun Fee Smulders, kende ta cerca di obtene su titulo como doktor na Wageningen University & Research y tambe ta autor principal di e investigacion aki. “Durante algun tempo e studiante di Master of Science Naomi Slikboer a sigui e seritonan aki, y el a nota presencia di tanto kimakima como yerba di lama invasivo na Corsou. El a descubri cu na cuminsamento tabatin hopi kimakima riba e seritonan, pero cu na final mayoria di e seritonan tabatin yerba di lama invasivo ta crece riba nan.”

Kimakima ta muda mas biaha

Researching the habitat of the upside-down jellyfish (Source: Erik Wurz) Photo: Erik Wurz

Pa motibo di binida di e yerba di lama, e kimakimanan mester muda mas biaha y posiblemente nan ta perde nan habitat. Mas aleu e investigadonan ta spera cu interaccion entre e yerba di lama invasivo y e seritonan lo percura pa un cama di yerba di lama dinamico y instabil, loke ta desbentahoso pa e yerba di lama indigeno balioso. Smulders: “Ta importante pa vigila e especie exotico aki bon y investiga su influencia riba tanto e especienan indigeno como riba henter e paisahe bou di lama.”

Mas informacion

E articulo Battle for the mounds: Niche competition between upside-down jellyfish and invasive seagrass den e revista cientifico Ecology.

DCNA

Dutch Caribbean Nature Alliance (DCNA) ta sostene comunicacion cientifico y alcanse den region Caribe Hulandes pa medio di haci informacion cientifico relata na naturalesa disponibel den un forma mas amplio, via entre otro Dutch Caribbean Biodiversity Database, e plataforma di noticia BioNews di DCNA y via prensa. E articulo aki ta contene resultado di un di e investigacionnan cientifico ey, pero e investigacion mes no ta un investigacion di DCNA. No por deriva ningun derecho for di e contenido. DCNA no ta responsabel pa e contenido y e consecuencianan (in)directo cu ta surgi  pa motibo di publicacion di e articulo aki.

 

 

Published in BioNews 62

 

Date
2023
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Curacao
Author

Shifting Seagrass Cues for Conch

Dutch below

The Caribbean Netherlands Science Institute, partnering with the Queen Conch Lab at the Florida Atlantic University is exploring the impacts of shifting seagrass species composition on local queen conch populations.  Queen conch depend heavily on native seagrass throughout their lifecycle, so the decline of native meadows could threaten conchs not only on St. Eustatius, but throughout the Caribbean region.

Queen conch are an iconic species for the Caribbean. In addition to their beautiful shell, queen conch play an important part in local cuisine as well as a role in seagrass grazing, keeping algae growth under control.  Queen conch are dependent on native seagrasses throughout their life cycles.  In fact, conch start off as microscopic free-floating larvae, found throughout the water column.   After about 21 days of swimming around, cues from their environment, namely native seagrass beds, tell them it’s time to settle and morph to a sand dwelling grazer.

The problem

Unfortunately, native seagrass around St. Eustatius and other (Dutch) Caribbean islands are being threatened by an invasive species from the Red Sea- Halophila stipulacea.  This new seagrass creates a completely different habitat, which affects how the ecosystem functions which could lead to changes in the composition and abundance of associated species (such as the queen conch). It is unclear if these invasive species offer the same cues to the conch larvae as their native counterparts.  To better understand this impact, a new project funded by World Wildlife Fund INNO-fonds and SPAW Regional Activity Center, led by the Caribbean Netherlands Science Institute partnering with Megan Davis from the Harbor Branch Oceanographic Institute at the Florida Atlantic University, is exploring these impacts.

Queen conch. Photo credit: Marion Haarsma

The Project

The first step of the project is to collect eggs from wild queen conch.  The female Queen conch lays her eggs in a thin sticky thread-like casing. This thread bundles together into an egg mass, often covered in sand so it can be very difficult to find. Each thread contains millions of eggs, so only a small portion of this egg mass (size of a 25 cent coin) is needed for the experiment. Once collected the eggs are transported to a lab where they can be placed in a tank to be monitored daily. After 4-5 days the eggs will hatch, releasing many microscopic conch larvae into the tank.

Time to Hatch

Once the eggs hatched, they are moved in small batches to individual beakers so they can be easily fed and monitored. Once they reach about 1 mm in length they are almost ready for their metamorphosis, about 21 days. The final stage of the project is to introduce various cues to the larvae to see how they respond.  In total four different cues will be used, in various combinations.  These cues include two native seagrasses, the invasive seagrass as well as that of bare sand.  After introduction, the conch larvae will be checked throughout the following week to see how they develop.

Want to know more about this project? Follow along with lead scientist, Dr. Kimani Kitson-Walters and check out the following vlog.

Updates to this project will also be featured in future BioNews articles.

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 contains the results of one of those scientific studies but the study itself is not a DCNA study. 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.

 

 

Het Caribbean Netherlands Science Institute dat samenwerkt met het Queen Conch Lab van de Florida Atlantic University, onderzoekt de gevolgen van een veranderende samenstelling van zeegrassoorten op lokale kroonslakpopulaties. Kroonslakken zijn gedurende hun hele levenscyclus sterk afhankelijk van inheems zeegras, dus de achteruitgang van inheemse velden kan een bedreiging vormen voor de kroonslak, niet alleen op Sint Eustatius, maar in het hele Caribische gebied.

De kroonslak is een iconische soort voor het Caribisch gebied. Naast hun prachtige schelp spelen kroonslakken een belangrijke rol in de lokale keuken, evenals een rol bij het grazen van zeegras, waardoor de algengroei onder controle wordt gehouden. Kroonslakken zijn gedurende hun hele levenscyclus afhankelijk van inheems zeegras. In feite beginnen kroonslakken als microscopisch kleine, vrij zwevende larven, die overal in de waterkolom te vinden zijn. Na ongeveer 21 dagen rondzwemmen, vertellen signalen uit hun omgeving, voornamelijk inheemse zeegrasvelden, hen dat het tijd is om zich te vestigen en te veranderen in een grazer die in het zand leeft.

Het probleem

Helaas wordt het inheemse zeegras rond Sint Eustatius vervangen door een invasieve soort uit de Rode Zee. Dit nieuwe zeegras creëert een compleet ander leefgebied, wat invloed heeft op het functioneren van het ecosysteem en kan leiden tot veranderingen in de samenstelling en overvloed van verwante soorten (zoals de kroonslak). Het is onduidelijk of deze invasieve soorten dezelfde aanwijzingen geven aan de kroonslak als hun inheemse tegenhangers. Om deze impact beter te begrijpen, onderzoekt een nieuw project, gefinancierd door het INNO-fonds van het Wereld Natuur Fonds en het SPAW Regional Activity Centre, geleid door het Caribbean Netherlands Science Institute in samenwerking met Megan Davis van het Harbor Branch Oceanographic Institute van de Florida Atlantic University, deze impact .

Kroonslak. Photo credit: Marion Haarsma

Het project

De eerste stap van het project is het verzamelen van eieren van wilde kroonslakken. De vrouwelijke kroonslak legt haar eieren in een dunne kleverige draadachtige omhulling. Deze draad bundelt zich tot een eimassa, vaak bedekt met zand, dus het kan erg moeilijk te vinden zijn. Elke draad bevat miljoenen eieren, dus slechts een klein deel van deze eimassa (ter grootte van een euro munt) is nodig voor het experiment. Eenmaal verzameld, worden de eieren naar een laboratorium vervoerd waar ze in een tank kunnen worden geplaatst om dagelijks te worden gecontroleerd. Na 4-5 dagen komen de eieren uit, waardoor veel microscopisch kleine larven in het aquarium terechtkomen.

Tijd om uit te komen

Zodra de eieren zijn uitgekomen, worden ze in kleine hoeveelheden naar individuele bekers verplaatst, zodat ze gemakkelijk kunnen worden gevoerd en gecontroleerd. Zodra ze ongeveer 1 mm lang zijn, zijn ze bijna klaar voor hun metamorfose, ongeveer 21 dagen. De laatste fase van het project is om verschillende signalen aan de larven te geven om te zien hoe ze reageren. In totaal worden vier verschillende signalen in verschillende combinaties gebruikt. Deze signalen omvatten twee inheemse zeegrassen, het invasieve zeegras en dat van kaal zand. De hierop volgende week worden de larven gecontroleerd op ontwikkeling.

Meer weten over dit project? Volg mee met hoofdwetenschapper Dr. Kimani Kitson-Walters en bekijk de volgende vlog: https://youtu.be/ioXYjohQCeg

Updates van dit project zullen ook worden vermeld in toekomstige BioNews-artikelen.

DCNA

De Dutch Caribbean Nature Alliance (DCNA) ondersteunt wetenschaps communicatie en bereik 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 bevat de resultaten van een van die wetenschappelijke onderzoeken, maar het onderzoek zelf is geen DCNA-onderzoek. 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 61

Date
2023
Data type
Media
Theme
Governance
Education and outreach
Legislation
Research and monitoring
Geographic location
St. Eustatius
Author

Invasive Seagrass and its effects on Juvenile Queen Conch

As invasive seagrass continues to expand and replace native species, populations such as the queen conch are seeing significant changes to their habitat and subsequent negative impact in food source availability. With potential consequence for the resilience of such species in a changing world. A recently published study from St. Barthelemy, St. Eustatius and St. Maarten, worked to understand how native and invasive seagrasses influence juvenile queen conch’s development by studying both dietary composition and growth rate.

 

This article was published in BioNews29

More information: Boman, E.M., Bervoets, T., de Graaf, M., Dewenter, J., Maitz, A., Meijer Zu Schlochtern, M.P., Stapel, J., Smaal, A.C., Nagelkerke, L.A.J., 2019. Diet and growth of juvenile queen conch Lobatus gigas (Gastropoda: Strombidae) in native, mixed and invasive seagrass habitats. MARINE ECOLOGY PROGRESS SERIES. Vol. 621: 143–154, 2019 https://doi.org/10.3354/meps12990

 

 

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
St. Eustatius
St. Maarten
Author

Invasive seagrass mega herbivore interactions

Invasive seagrass mega herbivore interactions
a study on the invasion of seagrass Halophila stipulacea in a Southern Caribbean lagoon affected by C. mydas grazing
In the Caribbean, the recent invasion of the seagrass species Halophila stipulacea has raised concerns regarding its impact on the invaded seagrass ecosystem and its associated flora and fauna. The main purpose of the experimental set-up was to understand the mechanisms and impacts of invasive species on a native seagrass in interaction with grazing impacts by the green sea turtle (C. mydas). The aims of the study were i.) to determine the colonization capacity of native seagrass species T. testudinum as affected by the presence of the invasive species (Halophila stipulacea) and vice-versa in a Caribbean lagoon (Lac Bay, Bonaire); ii.) To determine whether sexually and/or vegetatively colonization is affected by turtle grazing. and iii) to determine whether architectural properties of T.testudinum and H. stipulacea are affected by presence of other species and whether these are related to C. mydas grazing. For this study, four seagrass bed types were selected that naturally occur in the bay: (1) monoculture of T. testudinum, (2) monoculture of H. stipulacea , (3) mixed bed of H. stipulacea and T. testudinum and (4) mixed bed containing H. stipulacea, T. testudinum and S. filiforme. In each seagrass bed type, 12 experimental units were created divided over three experimental periods of six weeks. Within each unit, two patches of 150 x 150 mm were cleared of above and below ground biomass. Cages were placed over half of the cleared patches to prevent turtle grazing. After six weeks, recolonization of the patches by native species and invasive species were measured by resampling biomass. To assess whether turtle grazing changed architectural properties, measurements on length and width with and without grazing were taken. Lastly, lines around two T. testudinum turtle grazing plots were placed to measure the lateral expansion rate of the surrounding H. stipulacea patches.
Our results indicate that H. stipulacea is a ~11 times faster colonizer than T. testudinum. Effects of grazing on their colonization rate were different with T. testudinum colonization rate under C. mydas grazing being lower and H. stipulacea’s colonization rate being higher. These effects were not statistically proven, but strong trends were observed. The presence of other seagrass species did not seem to influence competitive abilities (colonization capacity and architectural properties). C. mydas grazing, on the other hand, clearly influenced T. testudinum’s architectural properties. Regarding T. testudinum’s grazing plots, an average lateral expansion of 0.35 cm day-1 by H. stipulacea was detected.
This study demonstrates that there is no direct competition between T. testudinum and H. stipulacea. It seems that H. stipulacea is colonizing areas unsuitable to T. testudinum. Sea turtle grazing creates less dense seagrass beds and therefore might further stimulate the expansion of H. stipulacea. The impact of the establishment of H. stipulacea on C. mydas is not yet clear: Even though it seems not to be the preferred seagrass species, C. mydas does graze on the invasive species in Lac Bay. It is, however, unknown how this new food resource will affect their fitness. Though the invasive may alter abiotic conditions in their habitat, the sea turtles may benefit from an extended cover of seagrass beds as the invasive seagrass is able to grow in places where native seagrass species currently cannot survive. It is recommended to keep monitoring changes and investigating the impact of H. stipulacea on the whole ecosystem.
 
Retreived from http://www.bonaireturtles.org on Aprile 13, 2015
 

Date
2014
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire

Continued expansion of the trans-Atlantic invasive marine angiosperm Halophila stipulacea in the Eastern Caribbean

Abstract:

Halophila stipulacea (Hydrocharitaceae) is reported for the first time from Aruba, Curaçao, Grenadines (Grenada), St. Eustatius, St. John (US Virgin Islands), St. Martin (France), and St. Vincent and the Grenadines, bringing the total number of known occurrences from eastern Caribbean islands to 19. Native to the Red Sea and western Indian Ocean, H. stipulacea spread to the Mediterranean Sea in the late 1800s and became established in the eastern Caribbean in 2002. The species has dispersed north and south of its first sighting in Grenada and now spans a latitudinal distance of 6° (>700 km), most likely facilitated by a combination of commercial and recreational boat traffic. The continuing range expansion of H. stipulacea indicates the species has successfully acclimated to surviving in the Caribbean environment, warranting further investigation into its ecological interactions with the indigenous seagrasses.

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Document
Journal
Geographic location
Aruba
Curacao
St. Eustatius
St. Maarten

BioNews 6 - June/July 2013

This month’s issue focuses on the development of the Dutch Caribbean Biodiversity Database, which addresses one of the biggest gaps for nature conservation on our islands – lack of access to relevant and reliable biodiversity information. The database, which was recently relaunched at www.dcbd.nl is the central repository for all biodiversity-related research and monitoring data, maps and literature for the six islands.

Amongst others, you will find in this sixth issue:

Date
2013
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
St. Eustatius
St. Maarten
Author

Results of Nature Foundation Research into invasive Seagrass H. stipulacea in the Simpson Bay Lagoon

Abstract:

In February 2013 the St. Maarten Nature Foundation confirmed the presence of Halophila stipulacea, an invasive seagrass, in the Simpson Bay Lagoon. The first unconfirmed, anecdotal report of a specimen of H. stipulacea being present in the Simpson Bay Lagoon dates back to 2010, when an EIA on the construction of the Lagoon Causeway was performed.

Extensive beds of H. stipulacea were found at three different locations: Big Key, Little Key and in the southeastern part of the Lagoon. St. Maarten is currently one of only four territories where the species has been found, thus research on controlling measures in the region are still in their infancy. A dedicated, detailed mapping project will show the real extent of distribution.

Management Recommendations:

One of the areas in Simpson Bay where most specimens were found was the planned location for the causeway. The dredging of this site in the near future will result in a definite reduction of H. stipulacea. However, this is not a solution that can be implemented everywhere. Therefore an alternative remedy has to be found to ensure that the species does not gain too much foothold within the ecosystem. The possibility of seeding areas with native grasses in an attempt to control the invasion is currently being investigated.

 

Date
2013
Data type
Research report
Theme
Research and monitoring
Geographic location
St. Maarten
Author