No abstract

Bermuda is an isolated 5560 ha chain of limestone islands on a 150 000 ha seamount located near 32°N, 64°W. Meadows of tropical and subtropical seagrasses, dominated by Thalassia testudinum and Syringodium filiforme, are found from inshore bays out to the inner edge of the rim reef that encircles the platform. Fine-scale computerized mapping and subsequent broad-scaled field assessment of seagrass meadows in Bermuda show that (1) meadows representing nearly one-quarter of the territory's total seagrass area in 1997 had declined by 2004, (2) net loss of seagrass meadows occurred at rim reef and lagoonal locations that are far-removed from anthropogenic disturbances, (3) the decline appears to have been in progress as early as 1996, and (4) both T. testudinum and S. filiforme meadows declined. Nearly 2100 ha of meadows were visible in a 1997 georeferenced mosaic of aerial photographs of the Bermuda platform. In 2004, 22 meadows that represented about 475 of the 900 ha of offshore seagrass identified in 1997 and earlier were absent or in obvious decline. The size and location of inshore and nearshore meadows, which are exposed to intense anthropogenic stresses and physical damage, varied over the same 7 yr but their total area has either remained unchanged or even increased. Processes contributing to the decline in offshore meadows have yet to be determined, but may include herbivory by juvenile green turtles and parrotfishes and below-normal productivity owing to a winter cold-water event correlated with a change in the North Atlantic Oscillation (NAO) in 1996. The potential consequences to Bermuda of the loss of nearly 500 ha of critical marine habitat are of extreme concern.

33The initial phase of a collaborative Ambient Monitoring Program (AMP) for the Strait of 34 Georgia (SoG) (Marine Environmental Research Vol. x, pp. ) has focused on the benthos, 35 sedimentary regimes, organic and contaminant cycling in subtidal regions of the strait. As part 36 of that project, we review the primarily subtidal benthic invertebrate faunal communities found 37 in the SoG, with particular reference to habitats and sediment conditions. This topic has not been 38 addressed in the primary literature for over 20 years. Benthic biota are the baseline sentinels of 39 the influence of natural and anthropogenic inputs to sediments. They are also a fundamental 40 component of the food chain at the seafloor, and their community ecology must be clearly 41 understood in order to predict how anthropogenic activities and climate change will affect our 42 coastal oceans. The purpose of this review is to provide context on habitats and biota in the SoG, 43 and to highlight topics and geographic areas where our knowledge of the benthos is limited or 44 lacking. 45 46

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/m 2 /d, 66.6gDW/m 2 , 2.62%/d, 1 481 gDW/m 2 , 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.

With 16 figures in the text)The shallow subtidal mactrid bivalve Muctrinulu reevesii is a deposit-feeder in the southern and south-eastern oceanic waters of Hong Kong. Buried obliquely, large quantities of fine sediment are taken into the mantle cavity and sorted on enormous labial palps. The small ctenidia probably have little value in collecting material, amounts taken in being too large. The mid gut is long and complexly folded inside the visceral mass. It is also capable of distension, although superficial visceral muscles maintain internal tonus. The rectum is narrow and creates compact faecal pellets.Most interest is in the ventral mantle margin which is, posterior to the pedal gape and the base of the inhalant siphon, united by a sheet of cuticle. There is no fourth pallial aperture. There are, however, two pairs of flaps extending along the posterior third of the internal ventral mantle surface. These arch over left and right mantle rejection tracts which transfer unwanted material to the base of the inhalant siphon for final expulsion. The mantle flaps prevent such material from being returned to the anterior end of the mantle cavity, for palp reprocessing, when new material arrives. They, thus, maximize sorting efficiency by separating unsorted from sorted and rejected material.Other mactrids have similar mantle flaps which they use in different ways, including the channelling of unwanted material to a fourth pallial aperture for expulsion, as in Lutruria lutruria. The Mactridae have thus evolved a unique method of increasing the efficiency of pseudofaecal waste rejection which has thereby facilitated the deposit-feeding lifestyle by the diverse representatives of this family.