NAVIGATION
This page is a sub-page of ObsSG, a top-level page on
the website Barbados Fringing Reefs and Seagrass Beds
(www.versicolor.ca/barbados).
Go to ObsSG for a list of other subpages in this section
of the website.
SUBPAGES OF THIS PAGE
– CC Blowouts
– CC Reef Flattening
NOTE: On July 1, 2024 Hurricane Beryl made landfall on Carriacou as a Category 4 hurricane; the island is still recovering.
DRAFTING
– Appendix B, A general description of seagrass beds in Barbados and Carriacou (Grenada) as observed 1967-1970 . In The origin of nitrogen and phosphorus for growth of the marine angiosperm Thalassia testudinum Konig.Patriquin, D.G. 1971. PhD Thesis, Marine Sciences Centre, McGill University, 193 pp. View a PDF of Appendix B.
– 
“Migration” of blowouts in seagrass beds at Barbados and Carriacou, West Indies, and its ecological and geological implications
DG Patriquin, 1975 Aquatic Botany Volume 1, Pages 163-189. View PDF
Abstract
Blowouts are grass-free depressions within seagrass beds at Barbados and Carriacou and reported in the literature to be common elsewhere in the Caribbean region. They are typically crescent-shaped in plan view with the convex side seaward, and are characteristic of elevated seagrass beds in regions of moderate to strong wave action. The seaward edge is steep and exposes rhizomes of Thalassia while the leeward edge slopes gently upward onto the seagrass plateau and is usually colonized by Syringodium. The general morphology of the blowouts, the zonation of organisms across them, and the existence at some blowouts of a lag deposit of cobble-sized material at the scarp base continuous with a rubble layer below the seagrass carpet suggested the blowouts “migrate” seaward. Measurements of erosion at the scarp and of advance of Syringodium onto the blowout floor over a period of one year confirmed this. It is estimated that in the region of blowouts any one point will be recurrently eroded and restabilized at intervals of the order of 5–15 years. Such processes limit successional development of the seagrass beds, disrupt sedimentary structures, and may result in deposits much coarser than those characteristic of the sandy seagrass carpet.
– Distribution and abundance of the invasive seagrass Halophila stipulacea and associated benthic macrofauna in Carriacou, Grenadines, Eastern Caribbean by Robert E. Scheibling1, David Patriquin, Karen Filbee-Dexter, 2018. In Aquatic Botany.
Abstract
The invasive seagrass Halophila stipulacea has spread throughout the eastern Caribbean since it was first recorded in Grenada in 2002. We quantified the distribution and abundance of H. stipulacea, and its associated macroinvertebrate fauna, in sampling stations and transects around the island of Carriacou (a nearby dependency of Grenada) in early 2016. Halophila stipulacea occurred in extensive monospecific stands (average bottom cover, 62%), or smaller mixed stands with native seagrass (Thalassia testudinum, Syringodium filiforme, Halodule wrightii), at 1–5 m depth in large bays along the leeward (west) coast. It was sparsely distributed on the more wave-exposed east and south coasts, usually in mixed patches with native seagrass. In leeward bays, H. stipulacea has largely replaced the native seagrass H. wrightii, providing a novel biogenic habitat for various filter-feeding invertebrates living within the turf-like leaf canopy (e.g., sponges, ascidians, bivalves, ophiuroids), and sea urchins (mainly Tripneustes ventricousus) and a microphagous sea star (Oreaster reticulatus) that graze upon it. Populations of the sea star consisted mainly of juveniles indicating the seagrass may serve as a nursery habitat for this endangered species. The spread of H. stipulacea along the leeward coast of Carriacou in recent years represents a community-level shift in the shallow subtidal zone, with attendant changes in habitat structure, species composition, and trophic interactions.
– Shifts in biodiversity and physical structure of seagrass beds across 5 decades at Carriacou, Grenadines by David Patriquin, Robert E. Scheibling, Karen Filbee-Dexter. 2024.
Abstract
Caribbean seagrass beds are facing increasing anthropogenic stress, yet comprehensive ground-level monitoring programs that capture the structure of seagrass communities before the 1980s are rare. We measured the distribution of seagrass beds and species composition and abundance of seagrass and associated macroalgae and macroinvertebrates in 3 years over a 47-year period (1969, 1994, 2016) at Carriacou, Granada, an area not heavily impacted by local human activity. Seagrass cover and physical parameters of fringing beds were measured in transects at high (HWE) and low wave energy (LWE) sites; frequency of occurrence of all species, and biomass and morphology of seagrasses, were measured at 100 m2 stations around the island. Losses in nearshore seagrass cover occurred at HWE but not LWE sites between 1969 and 2016 and were associated with increases in the seagrass-free inshore zone (SFI) and erosional scarps within beds. Total biomass did not vary across years although there were progressive changes in seagrass composition: a decline in the dominant Thalassia testudinum and concomitant increase in Syringodium filiforme, and establishment of invasive Halophila stipulacea in 2016 at LWE sites. Species richness and diversity of the seagrass community were highest in 1994, when 94% of macroalgae (excluding Caulerpa) were most abundant, and sea urchins were least abundant, compared to 1969 and 2016. Multivariate statistical analyses showed differences in community composition across the 3 years that were consistent with trends in urchin abundance. Increases in SFI and scarp number in seagrass beds at HWE sites occurred mainly after 1994 and likely were related to increased wave forcing following degradation of offshore coral reefs between 1994 and 2016. Our observations suggest that landward migration of seagrass beds with rapidly rising sea level in future will not be realized in reef-protected seagrass beds at Carriacou barring reversal in the processes that have caused reef flattening.
– Seagrass bed Flora & Fauna of Carriacou, Grenada 2016
iNaturalist Project “I am posting photos of seaweeds, seagrasses and epifauna from around Carriacou taken in Jan-Mar of 2016; a few in the same period in 2017, and 2019; with tentative IDs. Part of a scientific study repeating observations obtained in 1969 and 1994.”