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The influx of large numbers of alewife, Alosa pseudoharengus, into relatively small freshwater systems may have a considerable impact upon pre—established food chains and nutrient cycles. We estimate the total nutrient input to Pausacaco Pond, Rhode Island, USA, from alewives amounted to 0.43 g P, 2.7 g N, and 16.8 g/Cm2 over a 2—mo period. This is largely through mortality of the spawning fish, and to a lesser extent through excretion. These inputs were much greater than the eventual nutrient loss to the system through emigration of juvenile fish. In tank experiments using pond microcosms, the initial response to the addition of the fish was a large phytoplankton bloom and an increase in litter respiration. The phytoplankton bloom was short—lived, and the most lasting effort was an increase in production and respiration in the leaf litter. This increased production in the litter community would support a long lasting supply of insect and benthic invertebrate food for young fish. The respiration rate of autumn leaves incubated in alewife streams during the migration was significantly higher than that of leaves incubated simultaneously in a stream which had no alewife run. Respiration rates of leaves incubated in the same streams before the arrival of alewives did not differ significantly. The increase in litter respiration, an indication of microbial and invertebrate activity on the leaf surface, was attributed to the additional nutrients supplied by the fish.

ABSTRACT. Lagoons are highly productive coastal features that provide a range of natural services that society values. Their setting within the coastal landscape leaves them especially vulnerable to profound physical, ecological, and associated societal disturbance from global climate change. Expected shifts in physical and ecological characteristics range from changes in flushing regime, freshwater inputs, and water chemistry to complete inundation and loss and the concomitant loss of natural and human communities. Therefore, managing coastal lagoons in the context of global climate change is critical. Although management approaches will vary depending on local conditions and cultural norms, all management scenarios will need to be nimble and to make full use of the spectrum of values through which society views these unique ecosystems. We propose that this spectrum includes pragmatic, scholarly, aesthetic, and tacit categories of value. Pragmatic values such as fishery or tourism revenue are most easily quantified and are therefore more likely to be considered in management strategies. In contrast, tacit values such as a sense of place are more difficult to quantify and therefore more likely to be left out of explicit management justifications. However, tacit values are the most influential to stakeholder involvement because they both derive from and shape individual experiences and beliefs. Tacit values underpin all categories of social values that we describe and can be expected to have a strong influence over human behavior. The articulation and inclusion of the full spectrum of values, especially tacit values, will facilitate and support nimble adaptive management of coastal lagoon ecosystems in the context of global climate change.

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In a 28 mo mesocosm experiment, levels and patterns of productivity and respiration were observed for a range of nutrient additions selected to provide a gradation from conditions in lower Narragansett Bay, Rhode Island, USA, to maximum impact for a n urban estuary receiving present day levels of sewage effluents. For a 32-fold increase in nutrients, system apparent production increased by only a factor of 3 5. Seasonal patterns of autotrophy during the winter-spring diatom bloom a n d heterotrophy during summer and early fall occurred at all treatment levels. With the exception of the 8 X treatment, all treatments above 2 X had a greater respiratory demand in the water column than the benthos. The highest treatment mesocosm (32 X ) went briefly anoxic during the second summer of the experiment during a period when little productivity was occurring in the water column.

Which nutrients limit primary production in coastal marine environments? Using large (13 000 1) mesocosms with sediments we explored nutrient limitation in Narragansett Bay, Rhode Island, USA, over a 9 wk period. Separate and combined additions of phosphorus and nitrogen were made to the enclosures. Phytoplankton biomass, daytime whole system oxygen production and nighttime whole system respiration showed an approximately 5-fold increase in nitrogen and nitrogen + phosphorus treatments, whereas phosphorus treatments had somewhat lower phytoplankton biomass and metabolism than controls. In these whole system experiments nitrogen was the nutrient most limiting to primary production.