Caribbean-wide, long-term study of seagrass beds reveals local variations, shifts in community structure and occasional collapse.

The CARICOMP monitoring network gathered standardized data from 52 seagrass sampling stations at 22 sites (mostly Thalassia testudinum-dominated beds in reef systems) across the Wider Caribbean twice a year over the period 1993 to 2007 (and in some cases up to 2012). Wide variations in community total biomass (285 to >2000 g dry m(-2)) and annual foliar productivity of the dominant seagrass T. testudinum (<200 and >2000 g dry m(-2)) were found among sites. Solar-cycle related intra-annual variations in T. testudinum leaf productivity were detected at latitudes > 16°N. Hurricanes had little to no long-term effects on these well-developed seagrass communities, except for 1 station, where the vegetation was lost by burial below ∼1 m sand. At two sites (5 stations), the seagrass beds collapsed due to excessive grazing by turtles or sea-urchins (the latter in combination with human impact and storms). The low-cost methods of this regional-scale monitoring program were sufficient to detect long-term shifts in the communities, and fifteen (43%) out of 35 long-term monitoring stations (at 17 sites) showed trends in seagrass communities consistent with expected changes under environmental deterioration.

Decadal increase in seagrass biomass and temperature at the CARICOMP site in Bocas del Toro, Panama

The Caribbean Coastal Marine Productivity Program (CARICOMP) was launched in 1993 to study regional long-term interactions between land and sea, taking standardized measurements of productivity and biomass of mangroves, coral reefs and seagrasses. Since 1999 continuous measurements of seagrass (Thalassia testudinum) parameters as well as environmental data have been recorded in Caribbean Panama. Replicate stations were selected near the Smithsonian Tropical Research Institute in Bocas del Toro. Sediment cores and quadrants were placed there to estimate biomass and productivity, respectively. Mean values for productivity, standing crop, turnover rate, total dry biomass, and Leaf Area Index were 1.74gDW/m²/d, 66.6gDW/m², 2.62%/d, 1 481 gDW/m², and 4.65, respectively. Total dry biomass (shoots, rhizomes and roots) and LAI of T. testudinum increased significantly during the study period. Mean values for total rainfall, Secchi disk depth, sea surface temperature, and salinity were 3 498mm, 8.24m, 28.79°C, and 32.26psu, respectively. Sea surface temperature was the only environmental variable with a statistically significant change, increasing from 1999 to 2010. Correlation between sea surface temperature and T. testudinum parameters (total biomass and LAI) were both positive and significant. Human population has increased dramatically over the last ten years in Bocas del Toro region, increasing pressure (deforestation, runoff, wastewater) over coastal ecosystems (seagrasses, mangroves, coral reefs). Change in the abundance of T. testudinum may be linked to ocean warming, as a consequence to satisfy plant’s metabolic requirements, although other local factors need to be analyzed (reduced grazing and increased eutrophication). A further warming of the ocean could have a negative effect on T. testudinum population, increasing respiratory demands and microbial metabolism.

El Programa de Productividad Costera Marina del Caribe (CARICOMP) fue iniciado en 1993 para estudiar interacciones regionales a largo plazo entre la tierra y el mar, tomando mediciones estandarizadas de productividad y biomasa de manglares, arrecifes de coral y pastos marinos. Desde 1999 mediciones continuas de parámetros de pasto marino (Thalassia testudinum) así como datos ambientales han sido registrados para el Caribe de Panamá. Réplicas de estaciones fueron seleccionadas cerca del Instituto Smithsonian de Investigaciones Tropicales en Bocas del Toro. Núcleos de sedimento y cuadrantes fueron colocados para estimar biomasa y productividad, respectivamente. Valores promedio de productividad, biomasa foliar, tasa de recambio, biomasa total seca e Índice de Área Foliar fueron 1.74gDW/m²/d, 66.6gDW/m², 2.62%/d, 1 481 gDW/m², y 4.65, respectivamente. La biomasa total seca (haces, rizomas y raíces) e Índice de Área Foliar de T. testudinum incrementaron significativamente durante el periodo de estudio. Valores promedio de lluvia total, profundidad de disco de Secchi, temperatura superficial del mar y salinidad fueron 3 498mm, 8.24m, 28.79°C, y 32.26psu, respectivamente. La temperatura superficial del mar fue la única variable ambiental con un incremento estadísticamente significativo, de 1999 a 2010. La correlación entre la temperatura superficial del mar y los parámetros de T. testudinum (biomasa total y LAI) fueron tanto positivos como significativos. La población humana ha crecido dramáticamente durante los últimos diez años en la región de Bocas del Toro, incrementando la presión (deforestación, escorrentía, aguas negras) sobre los ecosistemas costeros (pastos marinos, manglares, arrecifes coralinos). Cambios en la abundancia de T. testudinum pueden estar ligados al calentamiento oceánico, como una consecuencia para satisfacer los requerimientos metabólicos de la planta, aunque es necesario analizar otros factores locales (reducción del pastoreo e incremento en la eutrofización). Un mayor calentamiento del océano puede tener efectos negativos en la población de T. testudinum, incrementando las demandas respiratorias y el metabolismo microbiano.

Decadal increase in seagrass biomass and temperature at the CARICOMP site in Bocas del Toro, Panama.

The Caribbean Coastal Marine Productivity Program (CARICOMP) was launched in 1993 to study regional long-term interactions between land and sea, taking standardized measurements of productivity and biomass of mangroves, coral reefs and seagrasses. Since 1999 continuous measurements of seagrass (Thalassia testudinum) parameters as well as environmental data have been recorded in Caribbean Panama. Replicate stations were selected near the Smithsonian Tropical Research Institute in Bocas del Toro. Sediment cores and quadrants were placed there to estimate biomass and productivity, respectively. Mean values for productivity, standing crop, turnover rate, total dry biomass, and Leaf Area Index were 1.74 gDW/m2/d, 66.6 gDW/m2, 2.62%/d, 1481 gDW/m2, and 4.65, respectively. Total dry biomass (shoots, rhizomes and roots) and LAI of T. testudinum increased significantly during the study period. Mean values for total rainfall, Secchi disk depth, sea surface temperature, and salinity were 3498 mm, 8.24 m, 28.79 degrees C, and 32.26 psu, respectively. Sea surface temperature was the only environmental variable with a statistically significant change, increasing from 1999 to 2010. Correlation between sea surface temperature and 7 testudinum parameters (total biomass and LAI) were both positive and significant. Human population has increased dramatically over the last ten years in Bocas del Toro region, increasing pressure (deforestation, runoff, wastewater) over coastal ecosystems (seagrasses, mangroves, coral reefs). Change in the abundance of 7 testudinum may be linked to ocean warming, as a consequence to satisfy plant's metabolic requirements, although other local factors need to be analyzed (reduced grazing and increased eutrophication). A further warming of the ocean could have a negative effect on T. testudinum population, increasing respiratory demands and microbial metabolism.