Dear colleagues,
Following up on the IUCN report of the Bonaire Marine Park, I would like to draw your attention to a recently published article in Bulletin of Marine Science:

“Coral community decline at Bonaire, Southern Caribbean”

Website: http://www.ingentaconnect.com/content/umrsmas/bullmar/pre-prints/8737;jsessionid=3qmvimw0g0nli.alice

Abstract:
We assessed the status of coral reef benthic communities at Bonaire, Netherlands Antilles, in December 2008 and January 2009 through aprox 5 km of photo transects taken at depths of 5, 10, and 20 m at 14 locations around the island. Univariate and multivariate analyses detected significant variation in benthic communities among depths and locations, as well as between leeward and windward sides of the island. Mean percentage cover of scleractinian corals ranged between 0.2 percent and 43.6 percent at the study sites and tended to be lowest at 5-m depth. The survey recorded 40 scleractinian coral species from 19 genera, within 10 families. Faviidae were by far the most abundant scleractinian family at all depths (predominantly Montastraea spp.), followed by Agariciidae at 20 and 10 m, and by Astrocoeniidae at 5-m depth. Macroalgal cover exceeded scleractinian coral cover at nearly all sites, averaging 34.9 percent (all samples pooled), compared with a pooled mean coral cover of 15.4 percent. Windward reefs were characterized by prolific growth of the brown algae Sargassum spp., and leeward reefs by growth of turf algae, Dictyota spp., Trichogloeopsis pedicellata (Howe) I. A. Abbott and Doty, and Lobophora variegata (Lamouroux) Womersley ex Oliveira. Damage from recent hurricanes was evident from the presence of toppled and fragmented corals, the movement of sand, and exposure of cemented Acropora cervicornis (Lamarck, 1816) rubble on the shallow reef platform. The combination of algal dominance and low to moderate coral cover are symptomatic of partly degraded reef systems, particularly as they coincide with elevated nutrients and reduced herbivory.

Regards,
Sander

Dr Sander Scheffers

Lecturer & Senior Research Fellow Southern Cross University
Honorary Research Fellow University of Queensland
Deputy Director Southern Cross Marine Science,
Associate Researcher Caribbean Research Institute for Management of Biodiversity (CARMABI), Curaçao (Netherlands Antilles)

Southern Cross University
PO Box 157, Lismore, NSW 2480, Australia
Email: sander.scheffers@scu.edu.au

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Coral-List mailing list

http://www.wm.edu/news/stories/2011/vims-study-propeller-turbulence-may-affect-marine-food-webs-123.php

by David Malmquist | April 25, 2011

A new study by researchers at the Virginia Institute of Marine Science shows that turbulence from boat propellers can and does kill large numbers of copepods-tiny crustaceans that are an important part of marine food webs.

The study-by VIMS graduate student Samantha Bickel, VIMS professor Kam Tang, and Hampton University undergraduate Joseph Malloy Hammond- appears in the March issue of the Journal of Experimental Marine Biology and Ecology.

The researchers don’t expect their findings to lead to any new “NoWake” signs in local waterways; their interest instead is to better understand how significant levels of propeller-induced mortality among copepods might affect local food webs in Chesapeake Bay and other highly trafficked waterways.

“Non-predatory mortality such as this is rarely considered in the literature,” says Bickel, “but it could be important for properly understanding zooplankton ecology and food-web dynamics in coastal and estuarine waters, particularly during summer months when recreational boating increases.”

Zooplankton are small drifting animals that consume algae and other microscopic floating plants. Copepods-shrimp-like crustaceans about the size of a rice grain-typically make up a major part of the zooplankton community and serve an important role by moving energy upthe marine food chain-from microscopic plants that are too small for most fish to eat up to larger game-fish and, ultimately,humans.

“If turbulence from boat propellers is killing off large numbers of copepods,” says Bickel, “it could be reducing the supply of food energy available to fish, and reducing zooplankton grazing of algal blooms.” “It’s like cutting down the number of zebras in a herd,” she adds. “That would affect not only the zebras, but also the grass they eat and the lions that eat them.”

This type of shift could potentially have a noticeable impact on marine food webs and water quality. “If a large portion of copepods are being killed, and if they sink down to the bottom, you could have additional high-quality organic material available for bottom-dwelling organisms to eat,” says Bickel. “If the amount is high enough, microbial decomposition could even perhaps contribute to development of localized low-oxygen ‘dead zones.'”

The researchers caution that there are untold millions of zooplankton in the world’s aquatic systems, so that when viewed at a global scale, the portion of copepods killed by boat-generated turbulence is probably minimal.

“The importance of turbulence as a source of mortality among copepods would be of much greater importance at a local scale,” saysBickel, “including highly trafficked areas near harbors and marinas, and within closed freshwater systems such as lakes.”

The research team studied propeller-induced mortality both in the field and laboratory. During the spring of 2010, they sampled copepods at three sites near the mouth of the Hampton River, a tributary of Chesapeake Bay. One site was a marina with numerous boats but minimal turbulence due to an imposed speed limit. The second was in a high-traffic area of a nearby navigational channel, where fast-moving boats generated considerable turbulence in their wakes. The third site was a tranquil shoreline opposite from the marina, with few boats and little or no boat-generated turbulence.

They compared the percentage of live and dead copepods collected from these sites using a dye that is only taken up by living copepods. The results of their comparison showed a much higher fraction of dead copepods in the channel (34%) than in the marina (5.9% dead) or along the shoreline (5.3%).

A field experiment in the York River near the VIMS campus confirmed the results of the Hampton River study. Here, they sampled copepods from within the wakes of passing boats, and again found a link between turbulence and mortality: the percentage of copepod carcasses increased from 7.7% outside the wakes to 14.3% inside the wakes.

The researchers were careful in both cases to minimize turbulence from their own vessel, using a rowboat for the Hampton River study and maintaining an idle during sampling in the York.

The team’s final experiment took place in the laboratory, where they exposed copepods to turbulence from a small motor calibrated to mimic the effects of different boat propellers. Their results again confirmed their earlier findings, with a clear link between mortality and increasing levels of turbulent energy.

Their experiments also show that natural turbulence from tides, currents, and waves is unlikely to stress or kill copepods other thanperhaps during an extreme storm event such as a hurricane ornor’easter.

Special thanks to Richard Charter

http://www.wri.org/publication/reefs-at-risk-revisited

This comprehensive report is well done and irreplaceable–an incredible resource.  DV

http://www.sciencemag.org/content/331/6022/1295.abstract
Science 11 March 2011:
Vol. 331 no. 6022 pp. 1295-1299
DOI: 10.1126/science.1200320

Abstract
A large fraction of atmospheric aerosols are derived from organic compounds with various volatilities. A National Oceanic and Atmospheric Administration (NOAA) WP-3D research aircraft made airborne measurements of the gaseous and aerosol composition of air over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico that occurred from April to August 2010. A narrow plume of hydrocarbons was observed downwind of DWH that is attributed to the evaporation of fresh oil on the sea surface. A much wider plume with high concentrations of organic aerosol (>25 micrograms per cubic meter) was attributed to the formation of secondary organic aerosol (SOA) from unmeasured, less volatile hydrocarbons that were emitted from a wider area around DWH. These observations provide direct and compelling evidence for the importance of formation of SOA from less volatile hydrocarbons.

Special thanks to Richard Charter