Resale or republication not permitted without written consent of the publisherOyster reefs reduce eutrophication by enhancing denitrification rates and assimilating nutrients into macrofauna.

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In their review "historical overfishing and the recent collapse of coastal ecosystems," Jeremy B. C. Jackson and colleagues argue for the "primacy" of overfishing in the collapse, in contrast to pollution, species introductions, climate change, diseases, and other human impacts (special issue on Ecology Through Time, 27 Jul., p. 629). They suggest that overfishing had the earliest impacts and was a necessary precondition for the occurrence of other maladies. Although we agree that fishing has contributed to major changes in coastal ecosystems, we believe Jackson and co-authors overstate the case for its primacy. The overfishing and nutrient pollution of coastal seas, for example, have frequently proceeded simultaneously and contributed to degradation synergistically (1).In Chesapeake Bay, as the authors point out, the process of eutrophication began with land clearing in the 18th century, well before the mechanized harvest of oysters in the late 19th century. Although most of the filtration capacity of oyster populations had been reduced by the 1930s, the dramatic intensification of hypoxia and the extensive loss of seagrasses occurred later, during the last half of the 20th century, associated with a more than doubling of the already elevated nitrogen loading (2).Recognizing that rebuilding oyster populations could help to mitigate planktonic overproduction due to nutrient pollution (3), the multistate Chesapeake Bay Program has established the ambitious goal of a 10-fold increase in oyster biomass. But restoration of oysters even to precolonial abundances is unlikely to eliminate algal blooms and hypoxia and recover seagrasses without also significantly reducing nutrient loading. Decreasing bottom-up stimulation and increasing top-down controls will be required.Although the degradation of oyster reefs by overfishing might have made oysters more susceptible to endemic diseases, a particularly virulent pathogen (Haplosporidum nelsoni) was introduced from a nonindigenous oyster host in the 1950s (4). This introduced disease now greatly limits the ability to reestablish oyster populations.Similarly, it is not likely that intact populations of large consumers, such as green turtles and sea cows, would have prevented the deleterious consequences of nutrient pollution, sedimentation, and other human-induced stresses on tropical seagrass ecosystems witnessed in the late 20th century in such regions as Australia (5) and Florida Bay (6). And there were no similar large consumers of temperate seagrasses, which have also undergone decline. Regardless of the historical sequence of human stresses, amelioration of multiple stresses must take a multi-pronged approach to restore coastal ecosystems. ResponseOur review is indeed about the deep historical roots of human degradation of a diverse suite of coastal marine ecosystems, caused by and preconditioned by fishing exploitation and attendant damage to biogenic marine habitats. The novelty of our study lies in its use of multiple associated disciplines, such as paleontology, ...

A century-long decline of the fishery for the Eastern oyster Crassostrea virginica (Gmelin, 1791) in Maryland and Virginia stimulated numerous efforts by federal, state, and nongovernmental agencies to restore oyster populations, with limited success. To learn from recent efforts, we analyzed records of restoration and monitoring activities undertaken between 1990 and 2007 by 12 such agencies. Of the 1,037 oyster bars (reefs, beds, or grounds) for which we obtained data, 43% experienced both restoration and monitoring, with the remaining experiencing either restoration or monitoring only. Restoration activities involved adding substrate (shell), transplanting hatchery or wild seed (juvenile oysters), bar cleaning, and bagless dredging. Of these, substrate addition and transplanting seed were common actions, with bar cleaning and bagless dredging relatively uncommon. Limited monitoring efforts, a lack of replicated postrestoration sampling, and the effects of harvest on some restored bars hinders evaluations of the effectiveness of restoration activities. Future restoration activities should have clearly articulated objectives and be coordinated among agencies and across bars, which should also be off limits to fishing. To evaluate restoration efforts, experimental designs should include replication, quantitative sampling, and robust sample sizes, supplemented by pre-and postrestoration monitoring.