Coastal & Estuarine Science News
| Volume 31 | Number 1-2 | |
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| CESN provides summaries of selected articles from the Federation's journal, Estuaries and Coasts. The summary articles emphasize management applications of the scientific findings. | ||
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Coastal Ecosystems Need Better Public Relations, Says Study
Coastal ecosystems -- including coral reefs, mangrove forests, seagrass meadows, and salt marshes -- are as important as they are imperiled, but they don’t get the public attention garnered by tropical rainforests. According to a recent study, scientific and public attention to these coastal ecosystems is not equitably distributed among the ecosystem types, either. While salt marshes cover the most area of the four, and seagrass meadows provide the most economic value per acre, it is the charismatic, colorful coral reefs that receive the most research and media attention. A survey of scientific publication records reveals that of the research publications on these ecosystems (approximately 30,000 total), 60% deal with coral reefs, and 11-14% are about mangroves, seagrasses, and salt marshes. The coral reef bias is even more apparent in popular media stories on these ecosystems, which can be considered a surrogate for public awareness and interest: 72.5% of media stories in surveyed media outlets (including such publications as the New York Times, National Geographic, CNN, China’s People Daily, Mexico’s El Universal, France’s Le Monde, and seven others) concerned coral reefs, 20% were on mangroves, 6.5% on salt marshes, and a tiny 1.3% on seagrasses.
These authors argue that more effective education and communication about these critical habitats, especially seagrass beds, is warranted. Scientists need to communicate with the public more effectively, utilizing cutting-edge educational methods. The public can become interested in seagrass meadows, the authors assert, if scientists can capitalize on their “unobtrusive charisma.” These efforts might have the happy side effect of encouraging more funding for research on these key ecosystems. Because, as Baba Dioum said, “For in the end, we will conserve only what we love. We will love only what we understand. We will understand only what we are taught.”
Source: Duarte, C. M., W. C. Dennison, R. J. W. Orth, and T. J. B. Carruthers. 2008. The charisma of coastal ecosystems: Addressing the imbalance. Estuaries and Coasts 31(2): 233-238. (Open Access)
If One Sediment Quality Assay is Good, Are Three Better?
What is the sediment quality in my estuary?
There are three basic approaches to answering this question, sometimes referred to as the sediment quality triad: measuring contaminant concentrations, determining sediment toxicity, and analyzing the benthic community. The prevailing notion about the triad is that three answers are better than one: no individual component of the triad can be used to predict the results of the other two, or to predict sediment quality on its own. The relationships among the three tests are far from simple, as contaminant concentrations are compared to benchmarks based on organism-level endpoints, toxicity tests measure effects at the organismal level, and benthic surveys examine community-level impacts.
A recent study compared the three methods using the extensive data collected by the EPA’s 1990-1993 EMAP survey of estuaries in the Virginian Province. Survey sites were divided into “affected” and “unaffected” categories based first on sediment contaminant concentration and then again based on toxicity testing. The two measures placed sites into the same category (affected/unaffected) only 25% of the time, lending support to the hypothesis that one assessment method is insufficient. When the results of benthic invertebrate surveys at affected and unaffected sites were compared, some benthic invertebrate results differed between groups while others did not. The two organism-level measures were found to be somewhat predictive of community-level effects. These results suggest that benthic invertebrate metrics may be used to validate adverse effects at sites identified as toxic based on chemical thresholds or toxicity bioassays.
Source: Griffith, M. B., and M. Kravitz. 2008. Relationships among exceedances of sediment guidelines, the results of ambient sediment toxicity tests, and community metrics in estuarine systems. Estuaries and Coasts 31(1): 101-114. (View Abstract)
“Thin Layers” Offer One Solution to the Cryptic Bloom Mystery
Harmful algal blooms can be stealthy. Often, a problem bloom goes undetected until sick or dead animals provide a clue that something is amiss in the ecosystem. These so-called “cryptic blooms” occur frequently in California’s Monterey Bay, prompting researchers there to try to determine why.
They hypothesized that bloom organisms may be concentrated in thin subsurface layers in the water column that are so narrow that they are easily overlooked by traditional sampling and monitoring methods. Using a bottom-mounted autonomous profiler, they conducted high-resolution vertical sampling of water quality parameters and phytoplankton. “Ground-truthing” and supplemental sampling was carried out concurrently by divers at specific depths as directed by results of the autonomous sampler. A thin layer was indeed detected using these methods. Ranging from 10 cm – 3 m in thickness, it persisted at the base of the pycnocline for the seven-day period of the survey. As hypothesized, the thin layer contained high concentrations of phytoplankton and bacteria, including suspects in the cryptic bloom case: the toxin-producing species Pseudo-nitzschia australis, at concentrations significantly higher than outside the layer. This layer, therefore, may serve as a “reservoir” for bloom formation. The high phytoplankton concentration may also act as an attractant to zooplankton and higher trophic levels, accounting for the appearance of ailing animals before blooms are evident.
While traditional sampling is unlikely to find these thin layers, the type of high-resolution sampling used in this study may help to identify thin layer phenomena in other coastal systems subject to cryptic blooms.
Source: McManus, M. A., R. M. Kudela, M. W. Silver, G. F. Steward, P. L. Donaghay, and J. M. Sullivan. 2008. Cryptic blooms: Are thin layers the missing connection? Estuaries and Coasts 31(2): 396-401. (View Abstract)
New Guidance for Expanding the Intersection of Management, Science, and Invasive Species
Because estuaries serve as centers of commerce, shipping, and other human activities, they tend to be magnets for introduced species. Evidence is constantly mounting that ecological, economic, and human health impacts of invasives are greater than previously thought. A recent review paper maintains that the gravity of the invasives problem warrants at least as much management and policy attention as that dedicated to other coastal issues, such as pollution or overharvesting. That management attention should take the form of proactive prevention, rather than costly eradication and control, whenever possible. Effective proactive control is currently hindered by substantial gaps at the intersection of science and policy, including a poor understanding of the potential adverse effects of invasives, trade restrictions, noncompliance with, and lack of enforcement of, existing regulations, and the political influence of regulated industries (shipping, aquaculture, etc.). A management-focused research agenda is proposed, which suggests that attention be paid to topics including the further study of impacts of invasives on communities and ecosystems, prevention and early detection techniques, and the ecological economics of invasion.
The authors suggest that invasive control programs in Australia and New Zealand should serve as models for the U.S. and Europe, where no centralized agency takes responsibility for the invasive species problem. Case studies of success stories are provided that will be enlightening to managers working on this critical issue.
Source: Williams, S. L., and E. D. Grosholz. 2008. The invasive species challenge in estuarine and coastal environments: Marrying management and science. Estuaries and Coasts 31(1): 3-20. (View Abstract)
Florida Bay Nutrients Not to Blame for Florida Keys Reef Losses
Like many coral reefs around the world, the reefs of the Florida Keys National Marine Sanctuary are in trouble. Scientists do not know why coral cover in the sanctuary is declining, but they have some ideas.
One common line of speculation posits that anthropogenic nutrient loads coming from Florida Bay through the many tidal passes between the Keys are to blame. Data to evaluate this suggestion have been lacking, but a recent study examined nutrient flux to the Sanctuary through Long Key Channel, one of the largest perforations in the Keys island chain. Although there was a net export of nutrients from Florida Bay to the reefs through the channel (approximately 3,850 tons of nitrogen per year and 63 tons of phosphorus per year), the concentration of nutrients flowing out of the bay is essentially the same as that going in, implying that no significant nutrient enrichment is occurring in the sanctuary’s waters in the vicinity of Long Key Channel. Larger-scale nutrient budgets indicate that offshore inputs of nutrients dwarf those that come from Florida Bay.
So, the mystery remains: what is killing corals in the Florida Keys National Marine Sanctuary? These results indicate that a more detailed nutrient loading model can, and should, be constructed for this area to help understand its complex nutrient dynamics and answer this question.
Source: Gibson, P. J., J. N. Boyer, and N. P. Smith. 2008. Nutrient mass flux between Florida Bay and the Florida Keys National Marine Sanctuary. Estuaries and Coasts 31(1): 21-32. (View Abstract)
Interactions of Birds, Crabs, and People in an Argentina Estuary
It sounds like a logic puzzle from a standardized test: given that people avoid crabs, birds avoid people, and some birds avoid crabs and some don’t, what is the impact of human disturbance on bird populations when there are abundant crab burrows on the shoreline?
In Argentina’s Mar Chiquita Biosphere Reserve, an important stop along the routes of many migrating shorebirds, burrowing crabs create a soft substrate that people prefer not to walk on. A survey in the area examined the impact of human disturbance on shorebird use at sites with and without crab burrows. Some of the shorebirds studied preferred to forage in the burrow areas, while others avoided the burrows, a distinction likely based on differing prey types and availability. The study was conducted at two locations differing in intensity of human use (one site was significantly less accessible by people than the other). Because people avoid the burrow areas, there is little human impact on birds that prefer them, like the two-banded plover. However, human disturbance did cause birds that prefer the un-burrowed substrate (yellowlegs, white-rumped sandpiper) to move to the suboptimal burrowed areas, potentially impacting their forage success. The magnitude of the impact of human presence varied by species depending on the birds’ tolerance for human approach. All six species studied varied their foraging behavior as humans approached, even if they did not fly away: some consumed less prey per minute, some spent more time walking and less time feeding in the presence of humans, and others spent more time handling prey.
For these shorebird species, foraging during their epic migrations is critical. This study shows that even minimal human disturbance can affect their energetics, possibly exacerbated and complicated by habitat factors such as the crab burrows discussed here. Because so many other ecosystems include burrowing animals like shrimp and crabs, these interactions should be taken into account by managers interested in protecting shorebirds in other estuaries.
Source: Botto, F., A. Mendez-Casariego, M. Valiñas, and O. Iribarne. 2008. Spatial heterogeneity created by burrowing crabs affects human impact on migratory shorebirds. Estuaries and Coasts 31(1): 134-143. (View Abstract)
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| Coastal and Estuarine Science News, a program of the Estuarine Research Federation, is funded by the Ocean and Coastal Protection Division of USEPA to strengthen the link between science and management in coastal systems. CESN is written by Nancy Steinberg. |