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 (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.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR

La conservation des zones humides à Trinidad et Tobago : Enjeux et défis

Rahanna Juman effectue d\u27abord une présentation historique, politique, démographique et géographique de Trinidad et Tobago. Elle se penche ensuite sur le troisième rapport de la CBD datant de 2006, mettant en exergue les principales menaces pour la biodiversité à Trinidad et Tobago, ainsi que les points pouvant faire obstacle à la gestion de la biodiversité comme à la mise en oeuvre de la convention

The structure and productivity of the Thalassia testudinum community in Bon Accord Lagoon,Tobago

The Thalassia testudinum dominated seagrass community in the Buccoo Reef/Bon Accord Lagoon Marine Park,measures 0.5 km² and is part of a contiguous coral reef,seagrass bed and mangrove swamp system in southwest Tobago.T.testudinum coverage,productivity and percent turnover rates were measured from February 1998 to February 1999 at four sample locations,while total T.testudinum biomass was measured at two locations in the lagoon from 1992-2002.Productivity and turnover rates varied spatially and seasonally. They were higher in the back-reef area than in the mangrove-fringed lagoon,and were lowest at locations near to a sewage outfall.T.testudinum coverage ranged from 6.6%in the lagoon to 68.5%in the back-reef area while productivity ranged from 3.9 to 4.9 g dry wt m-2 d-1 .Productivity and percentage turnover rates were higher in the dry season (January -June)than in the wet season (July -December).Productivity ranged from 3.0 in the wet season to 5.0 g dry wt m-2 d-1 in the dry season while percentage turnover rates ranged from 4.2%to 5.6%.Total Thalassia biomass and productivity in Bon Accord Lagoon were compared to six similar sites in the Caribbean that also participate in the Caribbean Coastal Marine Productivity Program (CARICOMP).This seagrass community is being negatively impacted by nutrient-enriched conditions.La comunidad de pastos marinos de Buccoo Reef/ Parque Nacional Bon Accord Lagoon,dominado por Thalassia testudinum,mide 0.5 km² y es parte de un complejo de arrecifes,lechos de pastos marinos y manglares en el suroeste de Tobago.La cobertura,productividad y tasa de recambio de T.testudinum fueron medidas de febrero 1998 a febrero 1999 en cuatro localidades,mientras que la biomasa total de T.testudinum fue medida en dos localidades en la laguna,entre 1992-2002.La productividad y la tasa de recambio variaron espacialmente y estacionalmente.Fueron mayores en la parte trasera del arrecife que en el manglar y la laguna del arrecife marginal,y fueron menores en localidades cerca de un emisario de aguas negras.La cobertura de T.testudinum tuvo un ámbito de 6.6%en la laguna a 68.5%en la parte trasera del arrecife, mientras que la productividad tuvo un ámbito de 3.9 a 4.9 g peso seco m-2 d-1.La productividad y las tasas de recambio fueron mayores en la época seca (enero a junio)que en la época lluviosa (julio-diciembre).La productividad tuvo un ámbito entre 3.0 en la época húmeda y 5.0 g peso seco m-2 d-1 en la época seca,mientras que las tasas de recambio variaron entre 4.2 y 5.6%.La biomasa total de Thalassia y la productividad en Bon Accord Lagoon fueron comparadas con seis sitios similares en el Caribe que también participan en el Programa de Productividad Marino-Costera del Caribe (CARICOMP).La comunidad de pastos de Bon Accord Lagoon está siendo afectada negativamente por enriquecimiento de nutrimentos

Biomass,litterfall and decomposition rates for the fringed Rhizophora mangle forest lining the Bon Accord Lagoon,Tobago

The mangrove forest that fringes the Bon Accord Lagoon measures 0.8 km² and is dominated by red mangrove (Rhizophora mangle ).This forest forms the landward boundary of the Buccoo Reef Marine Park in Southwest Tobago,and is part of a mangrove-seagrass-coral reef continuum.Biomass and productivity,as indicated by litterfall rates,were measured in seven 0.01 ha monospecific plots from February 1998 to February 1999,and decomposition rates were determined. Red mangrove above-ground biomass ranged between 2.0 and 25.9 kg (dry wt.)m-2 .Mean biomass was 14.1 ±8.1 kg (dry wt.)m-2 yielding a standing crop of 11 318 ±6 488 t. Litterfall rate varied spatially and seasonally.It peaked from May to August (4.2-4.3 g dry wt.m-2 d-1 )and was lowest from October to December (2.3-2.8 g dry wt.m-2 d-1 ).Mean annual litterfall rate was 3.4 ±0.9 g dry wt.m-2 d-1 .Leaf degradation rates ranged from 0.3%loss d-1 in the upper intertidal zone to 1%loss d-1 at a lower intertidal site flooded by sewage effluent.Mean degradation rate was 0.4 ±1%loss d-1 .The swamp produces 2.8 t dry wt.of litterfall and 12 kg dry wt.of decomposed leaf material daily.Biomass and litterfall rates in Bon Accord Lagoon were compared to five similar sites that also participate in the Caribbean Coastal Marine Productivity Programme (CARICOMP).The Bon Accord Lagoon mangrove swamp is a highly productive fringed-forest that contributes to the overall productivity of the mangrove-seagrass-reef complex.<br>El manglar que bordea la laguna de Bon Accord mide 0.8 km² y predomina el mangle rojo (Rhizophora mangle ).Este manglar es el límite terrestre del Parque Nacional Buccoo Reef en el suroeste de Tobago,y es parte de un continuo de mangles-pastos-arrecifes.En este trabajo se midió la biomasa y productividad,mediante la caída de hojas,y las tasas de descomposición en siete parcelas monoespecíficas de 0.01 ha,de febrero 1998 a febrero 1999.La biomasa sobre el suelo del mangle rojo se registró entre 2.0 y 25.9 kg (peso seco)m-2 .La biomasa promedio fue de 14.1 ±8.1 kg (peso seco)m-2 resultando en un recurso existente de 11 318 ±6488 t.La tasa de caída de hojas varió espacial y temporalmente.El máximo fue entre mayo y agosto (4.2-4.3 g peso seco m-2 d-1 )y el mínimo entre octubre y diciembre (2.3-2.8 g peso seco m-2 d-1 ).La tasa promedio de caída de hojas fue de 3.4 ±0.9 g peso seco m-2 d-1 .La tasa de degradación tuvo un ámbito de 0.3% pérdida d-1 ,en la parte superior de la zona intermareal a 1%pérdida d-1 en la parte inferior de sitios intermareales expuestos a aguas negras.La tasa de degradación promedio fue de 0.4 ±1%pérdida d-1 .Este manglar produjo 2.8 t peso seco de hojas y 12 kg peso seco de hojas descompuestas. La biomasa y las tasas de caída de hojas en Bon Accord fueron comparadas con otros cinco sitios que participan en el Programa del Caribe de Productividad Marino Costera (CARICOMP).El de la laguna de Bon Accord es un manglar marginal altamente productivo que contribuye a la productividad total del complejo mangles-pastos-arrecifes

Total (above- and below-ground) biomass of the principal components of the community per sampling station grouped per site.

<p>Other grass: species of seagrass other than <i>Thalassia testudinum</i>, mostly <i>Syringodium filiforme</i>. Somatic (decalcified) above-ground weight of the calcareous algae is considered. The boxes and bars represent inter-annual variation, and stations with only one sampling event are excluded. The digits above the bars in the bottom graph indicate N (the number of sampling years). M median of fleshy algae at site 5-station 13. See legend of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone-0090600-g002" target="_blank">Fig. 2</a> for further explanation.</p

Annual leaf productivity of <i>Thalassia testudinum</i> per sampling station.

<p>The stations are grouped per site (underlined, 1–6 stations per site), and stations only sampled during one season are excluded. The boxes and vertical bars represent inter-annual variation. The horizontal lines correspond with the median values, 50% of the cases are within the box limits and the vertical bars indicate the smallest or largest values that are not outliers, • represent values more than 1.5 box lengths from lower/upper box limit, and * represent values more than 3 box-lengths from lower/upper box limit. The digits above the bars indicate N (the number of sampling years). Grey bars represent stations that were not included in the long-term analysis.</p

Deviations from general mean leaf productivity (ΔP) of <i>Thalassia testudinum</i> per station during High growth season (May-September at site 1 and 2, March –August at all other sites) and Low growth season (October-April at sites 1 and 2, September-February at all other sites).

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600.s006" target="_blank">Table S4</a> for significance differences of ΔP. Only stations with at least 10 sampling events were included. Numbers above the X-axis indicate site number, and the minor ticks indicate the different sampling stations at those sites.</p

Significant long-term trends in seagrass attributes and community parameters at CARICOMP monitoring stations across the nine sites that showed changes consistent with deterioration of the environmental conditions.

<p>The broken smoothed lines connect annual average values and serve to illustrate the inter-annual variability in the data. Data from all samples per year (N = 4-9, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600.s005" target="_blank">Table S3</a>) were used to determine the regression lines (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600.s008" target="_blank">Table S6</a>). D. For Site14, the relationship was determined for the more persistent <i>Syringodium filiforme</i>.</p

Long-term trends at CARICOMP seagrass stations, including observations on disturbances.

<p>Biomass: total above-ground biomass of the community; Rel abund: relative abundance (biomass) of faster growing seagrass and algal species; Other seagrass: seagrass species other than <i>Thalassia testudinum</i> (mostly <i>Syringodium filiforme</i>); % Above/Total Biomass: percentage of above-ground of total biomass of <i>T. testudinum</i> (<i>S. filiforme</i> for site 14, because <i>T. testudinum</i> was absent in later years at station 33); Productivity: productivity of leaves of <i>T. testudinum</i>. ??? Collapse of seagrass bed, * seagrass beds showed changes that potentially indicate with human-induced environmental deterioration. Trends: <b>I</b> increase, <b>D</b> decrease, n without change, - not determined, <b>^N</b> expected change due to increasing nutrient load, <b>^T</b> expected change due to increasing turbidity, <b>^NT</b> expected change due to either increasing turbidity or nutrient load, changes without symbol were not consistent with expectations of water quality deterioration (See text for further explanation). Conditions at the beginning of monitoring: PRIST (relatively) pristine (undisturbed by humans); INT Moderate disturbance; DIST Disturbed (eutrophication, terrestrial runoff, or overfishing, from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-CARICOMP1" target="_blank">[26]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-CARICOMP2" target="_blank">[29]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-JordnDahlgren1" target="_blank">[47]</a>). See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600.s008" target="_blank">Table S6</a> for information on regression lines. Source: 1. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Murdoch1" target="_blank">[48]</a>, 2. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Fourqurean5" target="_blank">[49]</a>, 3. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Szmant1" target="_blank">[50]</a>, 4. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Fourqurean6" target="_blank">[51]</a>, 5. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-CARICOMP2" target="_blank">[29]</a>, 6. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Carruthers1" target="_blank">[52]</a>, 7. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-RodrguezMartnez1" target="_blank">[33]</a>, 8. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-VanTussenbroek2" target="_blank">[53]</a>, 9. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Davis1" target="_blank">[38]</a>, 10. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Koltes1" target="_blank">[44]</a>, 11. Pers. Obs. K. Koltes, 12.Pers.Obs. H.A Oxenford, 13. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-RodrguezRamrez1" target="_blank">[54]</a>, 14. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-RodriguezRamrez1" target="_blank">[55]</a>, 15. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Fonseca2" target="_blank">[56]</a>, 16. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-Corts1" target="_blank">[57]</a>, 17. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090600#pone.0090600-DCroz1" target="_blank">[58]</a>.</p