Aquatic Botany

Range expansion of Marinomyxa marina, a phytomyxid parasite of the invasive seagrass Halophila stipulacea, to the Caribbean

Abstract

Halophila stipulacea, a small seagrass species native to the Indo-Pacific, is a Lessepsian migrant and a high-profile invader that has successfully colonized two exotic regions, the Mediterranean (first observed in 1894) and the Caribbean (2002). In 1961, an intracellular phytomyxid parasite, Marinomyxa marina (SAR: Rhizaria: Endomyxa: Phytomyxea) was discovered in the petioles of H. stipulacea in the Red Sea, and three decades later, it was reported off the coast of Sicily (Mediterranean), suggesting parallel migration of the two organisms. In 2018, infected petioles of H. stipulacea were also observed in St. Eustatius (Caribbean), but the identity of the causative agent remained unresolved. Here, we provide information on four new localities of phytomyxid-infested populations of H. stipulacea in Greece (Mediterranean), and Bonaire and Martinique (Caribbean), including notes on infection prevalence and seasonal dynamics. Using the 18S rRNA barcoding gene, we bring molecular evidence that the disease is caused by a genetically uniform variant of M. marina at all the examined sites. We conclude that the parasite is now widespread throughout both invaded regions and has been present in the Caribbean since 2013 at the latest. For the first time, the production of fruits in infected plants is observed, indicating a non-lethal nature of the symbiosis. While the arrival of M. marina to the Caribbean is unlikely to alleviate the current invasiveness of H. stipulacea, we emphasize the need for its further monitoring since the host-specificity and general biology of seagrass-associated phytomyxids are still poorly understood.

 

 

View full text https://www.sciencedirect.com/science/article/abs/pii/S0304377022000663

Date
2022
Data type
Scientific article
Journal
Geographic location
Bonaire

Fish grazing enhanced by nutrient enrichment may limit invasive seagrass expansion

The success of invasive macrophytes can depend on local nutrient availability and consumer pressure, which may interact. We therefore experimentally investigated the interacting effects of nutrient (nitrogen and phosphorus) addition, the exclusion of large herbivorous fishes and mimicked grazing on the expansion rates of the invasive seagrass Halophila stipulacea. The experiments were established on Bonaire and Aruba, two islands in the southern Caribbean, which differ in fish community structure. We observed that multiple Caribbean fish species feed on H. stipulacea. At both study sites, nutrient enrichment decreased invasive leaf carbon:nitrogen ratios. However only on Bonaire, where herbivore fish abundance was 7 times higher and diversity was 4.5 times higher, did nutrient enrichment result in a significant reduction of H. stipulacea expansion into native Thalassia testudinum meadows. This effect was likely due to increased herbivory on nutrient enriched seagrass leaves, as we found that excluding large herbivorous fish (e.g. parrotfish) doubled invasive expansion rates in bare patches on Bonaire. On Aruba, H. stipulacea expansion rates were higher overall, which coincided with lower abundances and diversity of native fishes, and were limited by mimicked fish grazing. We suggest that top-down control by the native fish community may counteract eutrophication effects by increased grazing pressure on nutrient-rich invasive seagrass leaves. We conclude that diverse and abundant herbivore communities likely play an important role in limiting invasion success and their conservation and restoration may serve as a tool to slow down seagrass invasions.

Date
2021
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Aruba
Bonaire

A quantitative study of the seagrass and algal meadows of the Spaanse Water, Curaçao, the Netherlands Antilles

The Spaanse Water is a relatively turbid, 3.19 km2 inland bay of virtually oceanic salinities and contains the largest seagrass, algal and mangrove areas of the Curaçao Underwater Park. During 1989 and 1990, a quantitative community assessment of the larger attached flora and fauna of the seagrass and algal meadows of the bay was conducted at 151 6 m2 stations using a quadrat sampling technique.

A total of 13 different assemblages were distinguished. Shallow assemblages were dominated by Thalassia testudinum and Halimeda opuntia. As depth increased and light levels decreased, Thalassia gave way to increased coverages of especially H. opuntia, H. incrassata, Cladophora sp. and Caulerpa verticillata. In areas with significant availability of hard substrate an assemblage characterised (though not dominated) by corals was found at depths of 0–2 m, while sponges were concentrated at depths of about 4 m. The richest assemblages were found in shallow areas with high light levels and where a mix of both hard and soft substrate occurred. Assemblages with the lowest species richness were typically associated with low light intensities, soupy muds or homogeneous sandy sediments of high grain size.

Date
1996
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Phytomyxid infection in the non-native seagrass Halophila stipulacea in St Eustatius, Caribbean Netherlands

Highlights

 

• First record of phytomyxid infection in H. stipulacea in the Caribbean.

• Morphological changes to leaves, roots and internodes in infected fragments.

• Possible wide-spread Caribbean distribution of phytomyxid infection in H. stipulacea.   

Phytomyxids are a monophyletic group of biotrophs/parasites of a variety of organisms including seagrasses with a wide distribution range that includes the Caribbean. The seagrass Halophila stipulacea, native to the Indo-Pacific and Red Sea, is a known host for phytomyxids in the Mediterranean. However, to date phytomyxid infection has not been reported for H. stipulacea in the Caribbean. Infection in H. stipulacea is characterized by swelling of the leaf petioles due to gall formation, and coloration of these galls varies depending on the stage of maturity. H. stipulacea fragments with an apparent phytomyxid infection as well as uninfected fragments were collected in St Eustatius, north-eastern Caribbean, for comparative biometric analysis. Measurements of leaf length, leaf width, internode and root length were taken. Infected H. stipulacea fragments were significantly smaller than uninfected fragments across all biometrics measured, and exhibited similar gall colorations and swelling of the leaf petioles previously described for H. stipulacea in the Mediterranean. Based on our observations, the apparent infection in H. stipulacea fragments on St. Eustatius is likely caused by a phytomyxid parasite and is the first record of phytomyxid infection of this seagrass species in the Caribbean.

 

Date
2020
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
St. Eustatius

Patterns of distribution and drivers of change in shallow seagrass and algal assemblages of a non-estuarine Southern Caribbean mangrove lagoon

Shallow marine macrophyte communities serve key roles in the tropical coastal ecosystem but are undergoing large and rapid deterioration worldwide, as is also the case in the non-estuarine mangrove lagoon of Lac Bay, Bonaire, in the Southern Caribbean. To help better understand both the drivers of assemblage structure and potential consequences of the changes taking place in the bay, we here quantify and describe the distribution of algal and seagrass assemblages along the environmental gradient from the turbid, inner mangrove pools to the clear, open bay conditions, based on 98 randomly-chosen, 4 m2 survey plots. Seven assemblages were described along this land-to-sea gradient, five of which were dominated by marine macrophytes, one by sponges and one by a polychaete. With exception of the hypersaline backwaters which were devoid of benthic macrophyte vegetation, isolated mangrove pools showed the lowest total benthic cover, species richness and biodiversity of all habitats. Salinity and substrate particle-size composition accounted for most variation between the different assemblages and appear to be the key known determinants of assemblage composition. We developed a conceptual model to help disentangle the relationship between and the relative roles of the two principal drivers, as part of a cascade of effects which ultimately result from terrestrial run-off into the bay as mediated by mangrove encroachment into the bay. The model links spatial patterns to ongoing processes and implies that the assemblage patterns described are not only a reflection of, but also allow prediction of how the assemblages develop through time.

Date
2019
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire
Author

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