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.
July 2011
Contents
Tampa Bay Leads the Way in Using Biotope Mosaic Approach to Management
Cause and Effect in the Baltic Sea: What Controls Phytoplankton Communities?
Shedding Light on Water Column Optical Properties and Seagrass Beds in Florida Bay
Weighing Issues of Scale in Monitoring Programs: Study Uses Nested Approach to Monitor Seagrass Beds
Tampa Bay Leads the Way in Using Biotope Mosaic Approach to Management
Humans are an inextricable part of coastal ecosystems, and coastal managers know they will not make much headway if they aim to restore ecosystems to some pristine state that existed before people came on the scene. So what are the appropriate benchmarks and goals for estuarine restoration? A novel approach to answering this question, easily transferable to other systems, has been used successfully by the Tampa Bay Estuary Program (TBEP).
TBEP’s management framework involved developing estuarine restoration goals based on the state of habitat landscapes, or biotopes (seagrass beds, mangrove forests, etc.) required by key estuarine faunal groups. The method seeks to restore ratios of these habitat types such that the mosaic of biotopes resembles a benchmark point in time. In this case, the baseline condition was defined as 1950, for both scientific and public outreach purposes. The program’s ecological priorities are to “Restore the Balance” (the slogan of the project) of biotopes using the ratio approach, as well as to protect and restore total acreages of important habitats. Quantifiable goals (e.g., “Restore 95% of the seagrass area that was present in 1950”) were established by committees of scientific experts and a diverse group of stakeholders using a consensus-based process. In order to meet the stated goals, a range of adaptive management strategies has been employed.
This approach has met with success in Tampa Bay. Over 2,200 ha of high-value estuarine biotope have been regained since this strategy has been adopted. The authors also point out that the approach can be integrated into other management approaches, such as the Biological Condition Gradient approach and ecosystem-based management.
Source: Cicchetti, G. and H. Greening. 2011. Estuarine biotope mosaics and habitat management goals: An application in Tampa Bay, FL, USA. Estuaries and Coasts 34(July 2011). DOI: 10.1007/s12237-011-9408-4.
Cause and Effect in the Baltic Sea: What Controls Phytoplankton Communities?
The value of a long-term data set was demonstrated by a recent study of phytoplankton communities in the Gulf of Riga, a semi-enclosed basin of the Baltic Sea. More than thirty years of monitoring data (collected from 1976-2008) were used to examine the relationships between phytoplankton communities and parameters related to nutrient loading, climate change, and overfishing.
The data and statistical analyses revealed that the spring bloom is most influenced by nutrient levels, particularly phosphorus, coming from the land. Therefore, the investigators say, limiting P loadings to the system at the watershed scale will help control the blooms and related eutrophication. Reducing nitrogen might affect summer blooms in this system, but it is not the primary driver of phytoplankton dynamics. Summer blooms appear to be driven by the alteration of the food web that has occurred as a result of overfishing, which had resulted in reduced grazing and an enhanced microbial loop. While fishing is less significant in the Gulf of Riga than in the Baltic Sea as a whole, fish populations in the Gulf are impacted by overfishing in the Baltic, particularly for sprat. Therefore, fisheries management on a regional scale will be needed to address this problem. Finally, the authors speculate that temperature increases brought about by climate change will likely result in a shift from dinoflagellates to chlorophytes in the summer, but the implications of this change in terms of the food web are not known.
This study shows how valuable long-term data such as that used here can be for gaining insights into the processes that control coastal systems.
Source: Jurgensone, I., J. Carstensen, A. Ikauniece, and B. Kalveka. 2011. Long-term changes and controlling factors of phytoplankton community in the Gulf of Riga (Baltic Sea). Estuaries and Coasts 34(July 2011). DOI: 10.1007/s12237-011-9402-x.
Shedding Light on Water Column Optical Properties and Seagrass Beds in Florida Bay
The precipitous decline of critical seagrass beds in Florida Bay (30% decline throughout the 1980s and 1990s) has been attributed to many factors: disease, eutrophication, changes in salinity, and others. Although the chain of events that initiated the mass die-off is not fully understood, these plants have notoriously high light requirements, and water quality deterioration leading to light limitation is a leading cause of their decline throughout the world. Is light limiting in Florida Bay?
A recent study of the optical properties of the water column there mapped and quantified seagrass bed health at sites throughout the bay, and measured factors that scatter and absorb water column light. These attenuation factors tend to preferentially scavenge blue light, an important driver of photosynthesis. The authors found that seagrasses were absent or rare in areas where turbidity attributable to high levels of inorganic suspended matter caused excessive scattering of downwelling light. Light scattering by suspended carbonate sediment particles appeared to be the most important optical factor controlling light availability for seagrass beds.
Once a seagrass bed has been lost, regardless of the cause, the sediment-stabilizing function of the seagrasses themselves is also lost, leading to increased sediment suspension and, potentially a feedback loop making restoration or natural regrowth difficult. Therefore, seagrass restoration efforts must consider local physical processes (winds, currents) that can resuspend particles along with nutrient controls implemented to help reduce algal blooms (another factor that can cloud the water column), in order to maximize effectiveness.
Source: McPherson, M. L., V. J. Hill, R. C. Zimmerman, and H. M. Dierssen. 2011. The optical properties of Greater Florida Bay: Implications for seagrass abundance. Estuaries and Coasts 34(July 2011). DOI: 10.1007/s12237-011-9411-9.
Weighing Issues of Scale in Monitoring Programs: Study Uses Nested Approach to Monitor Seagrass Beds
Monitoring programs are critical to management, but also expensive. With a given number of dollars to execute an environmental monitoring program, should you measure a small number of parameters over a broad area, or a larger number of parameters over a more limited area? How can your limited funding and personnel be optimally distributed? A three-tiered framework for monitoring seagrass beds was recently tested in two estuaries in the northeast (Little Pleasant Bay on Cape Cod, MA and Great South Bay, NY). Existing seagrass mapping programs conducted by the states of New York and Massachusetts provided large-scale information on seagrass distribution, the “tier 1” data for this study. For “tier 2,” the investigators sampled two key properties of seagrass beds (percent cover and canopy height) at a large number of stations throughout the beds in the two estuaries. Tier 3 monitoring examined more parameters, but at a smaller number of locations.
The parameters monitored were chosen specifically to evaluate whether seagrass conservation objectives are being met. Statistical analyses were carried out to determine the number of samples needed to detect change (for example, four subsamples per hexagonal sampling station were adequate to estimate average percent cover on a bay-wide scale). Annual tier 2 and tier 3 monitoring required a total of three to 13 field days for a maximum of four people. Tier 3 monitoring data can help explain and even predict system-wide changes (e.g., a decline in biomass or shoot density might provide a warning that the entire seagrass meadow is under stress and might deteriorate in the future). One other advantage to this approach is that it easily points out where additional monies could be spent, should they become available. In this instance, the authors recommend adding tier 3 sites to help elucidate larger scale trends.
Generally, this survey found an improvement in the condition of seagrass resources in these two estuaries during the study period. The results suggest that this approach is an efficient and feasible way to detect and predict changes in seagrass beds, and can provide critical data to assess the success of multi-scale conservation objectives.
Source: Neckles, H. A., B. S. Kopp, B. J. Peterson, and P. S. Pooler. 2011. Integrating scales of seagrass monitoring to meet conservation needs. Estuaries and Coasts 34(July 2011). DOI: 10.1007/s12237-011-9410-x.
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