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Coastal & Estuarine Science News (CESN)

Coastal & Estuarine Science News (CESN) is an electronic publication providing brief summaries of select articles from the journal Estuaries & Coasts that emphasize management applications of scientific findings. It is a free electronic newsletter delivered to subscribers on a bimonthly basis.

January 2010


Shoreward Human Migration in Texas May Be Chasing Coastal Birds Away
Recovery of a Dutch Coastal Lagoon: Macrobenthos Lags, But Will Probably Catch Up
The Fall and Rise (and Fall and Rise) of Chesapeake Bay Eelgrass, and Strategies to Encourage Conservation and Recovery
Beach Grooming Makes Beaches Picturesque, but Does It Destroy Habitat?

Shoreward Human Migration in Texas May Be Chasing Coastal Birds Away

Every other day for 29 years and counting, a survey has documented every bird sighted along an 11.7 km stretch of Mustang Island, a barrier island on the Texas Gulf coast. The value of such an intensive, consistent, long-term data set is clear, especially since major anthropogenic changes have occurred on the island during that time frame. When the survey began, there were no large developments along the survey route, but by 2008 the landscape included numerous condominiums and residential communities.

What impact did this influx of human residents have on the bird species found on the island? A recent analysis of the data examined trends in the 28 most commonly-observed species in the survey, as well as in numbers of people and vehicles observed on the beach. The study found that as human disturbance increased over the study period (mean number of people on the beach increased five-fold), ten of the 28 species examined declined significantly, including four species of terns crucial to the coastal food web, and four increased significantly. Declines ranged from 34% to 87%. Notably, the brown pelican, removed from the endangered species list in November of 2009, increased in numbers by 586%.

The study could not determine whether the observed decreases represent loss of individuals or a shift in distribution to sites outside of the study area. Also, the diversity of declining species makes it difficult to ascertain the cause of the decline. However, similar trends in bird abundance have been observed in other surveys, and the authors believe that it is likely that a combination of population declines and displacement by human disturbance in the Mustang Island study area may explain the local trends. Whatever the reason, the loss or displacement of birds from this system could reverberate throughout the ecosystem, as crucial ecological functions of these species such as seed dispersal and scavenging could be curtailed.

Source: Foster, C. R., A. F. Amos, and L. A. Fuiman. 2009. Trends in abundance of coastal birds and human activity on a Texas barrier island over three decades. Estuaries and Coasts 32: 1079-1089. DOI: 10.1007/s12237-009-9224-2.

Recovery of a Dutch Coastal Lagoon: Macrobenthos Lags, But Will Probably Catch Up

In 1953, a disastrous coastal flood in the Netherlands killed about 1,800 people. In order to prevent a recurrence, the southwest coast was altered drastically: A series of semi- and fully-enclosed basins was created, including Lake Veere. Closed off from the North Sea in 1961, the lake served as a reservoir for winter runoff and a site for recreational activities in the summer. Over time, water quality declined severely in the eutrophied lake, and subsequent management steps actually made things worse. The condition of the lake deteriorated, compromising its value as a recreation site and a habitat for migratory birds, and so a further step was taken: a water gate (Katse Heule) was installed to reconnect the lake to the Eastern Scheldt estuary.

Monitoring programs collected water quality data and surveyed the macrobenthos in the lake before and during declining water quality, and after the gate installation. These surveys found that water quality improved after gate installation. Hypoxia and anoxia were reduced in some parts of the lake, and nutrient levels were reduced due to greater export (loadings remained the same). More improvement was observed at sites closer to the gate. With respect to the macrobenthos, the study found that the number of new and reappearing species (those that were found to be present for at least two years after having been absent for at least three sequential years) increased post-restoration, but the overall abundance and biomass of organisms did not change. The authors expect that restoration of the macrobenthos is simply lagging behind water quality improvements, as the limiting factors for those populations are likely related to recruitment and proximity of source populations, rather than water quality. They warn that full recovery could take years to decades more.

Source:  Wijnhoven, S., V. Escaravage, E. Daemen, and H. Hummel. 2010. The decline and restoration of a coastal lagoon (Lake Veere) in the Dutch delta. Estuaries and Coasts 33(January 2010). DOI: 10.1007/s12237-009-9233-1.

The Fall and Rise (and Fall and Rise) of Chesapeake Bay Eelgrass, and Strategies to Encourage Conservation and Recovery

With apologies to Rodney Dangerfield, seagrasses get no respect. While they have suffered losses similar to coral reefs and marshes, and are equally important ecologically and more widely distributed, they have received only a fraction of the media and scientific attention of those other habitat types. A recently-published paper provides a historical account of trends in mid-Atlantic seagrass beds and makes suggestions for further restoration, using Chesapeake Bay as its prime example.

Eelgrass populations in Chesapeake Bay crashed in the 1930s, the result of both a fungal disease outbreak and a hurricane. Beds rebounded in most areas, only to decline again throughout the late 1960s and 70s because of deteriorating water quality. Bay eelgrass came back again between 1984 and 1993, but is now once again disappearing largely due to declining water clarity.

There is some good eelgrass news: Eelgrass abundance is now one of the criteria for assessing attainment of Chesapeake water clarity goals, and multiple restoration efforts have taken place, transplanting both adult plants and seeds. While many of these efforts in the Chesapeake have failed, in Virginia’s coastal bays restoration has been successful for over a decade. Restoration success has increased along with our knowledge of these systems and with better site selection, but it will be critical to ensure that water quality is maintained at restoration sites, as well as at remaining beds. Research is also necessary in order to understand the multiple factors that can influence seagrass populations, from global climate change to shifts in higher trophic levels to human-induced threats such as fishery practices. The findings of this synthesis and other research can easily be applied to seagrass restoration projects around the world.

Source: Orth, R. J., S. R. Marion, K. A. Moore, and D. J. Wilcox. 2010. Eelgrass (Zostera marina L.) in the Chesapeake Bay region of mid-Atlantic coast of the USA: Challenges in conservation and restoration. Estuaries and Coasts 33(January 2010). DOI: 10.1007/s12237-009-9234-0

Beach Grooming Makes Beaches Picturesque, but Does It Destroy Habitat?

Some of those iconic southern California beaches are kept postcard-clean by the practice of beach grooming, in which heavy machines remove debris (both anthropogenic and natural, such as seaweed) from the sand and rake everything smooth. But it appears that these aesthetic elements of grooming come at an ecological cost. It has already been shown that what to humans is unsightly debris is actually habitat and food for a rich community of invertebrates and important foraging habitat for shorebirds. A recent study of groomed and ungroomed southern California beaches examined the additional impacts of grooming on maintenance of the coastal strand and foredune, populations and performance of native coastal plants, sand transport, and implications for foredune formation.

Grooming or raking directly altered the physical characteristics of the beaches. On groomed beaches unvegetated dry sand zones were four times wider than on ungroomed beaches, meaning that the vegetated strand habitat had been eliminated in groomed areas, and macrophyte wrack cover was significantly lower. Native plant abundance and richness were also significantly lower on groomed beaches compared to ungroomed beaches. Although seeds of native plants germinated equally well on experimental plots on groomed and ungroomed areas of beach, the number of seeds present in the seed bank and seedling survival to flowering stages was much lower in the seasonally groomed area. In fact, all seedlings in the groomed area died nearly a month before the initiation of seasonal grooming in late May.  Finally, rates of wind-driven sand transport were significantly higher in groomed plots, as compared to ungroomed plots where native plants or wrack left reduced sand transport.

Coastal strand and dune habitat is important not only to the plants and animals that nest and forage there, but also as the first line of defense against coastal storms.  These habitats are also increasingly squeezed between the forces of sea level rise and coastal development. The authors of this study suggest a management scheme that allows for stretches of beach that are left ungroomed year-round.

Source: Dugan, J. E. and D. M. Hubbard. 2010. Loss of coastal strand habitat in Southern California: the role of beach grooming. Estuaries and Coasts 33(January 2010). DOI: 10.1007/s12237-009-9239-8.