Images of oiled sea birds or otters being scrubbed clean dominate the news when an oil spill occurs in the marine environment. But what about impacts on the critical parts of the ecosystem we can’t see with the naked eye? A recent study of the sublethal effects of crude oil on estuarine phytoplankton communities concluded that low levels of exposure may reduce total biomass and alter community structure significantly.
Samples of the natural phytoplankton community taken from North Inlet, SC were placed in mesocosms suspended in the water column. Enclosures were dosed with two types of oil – Texas crude and oil from the Gulf of Mexico Deepwater Horizon spill – in varying concentrations and then incubated in situ for 33 hours. Chlorophyll a and other pigment concentrations were measured before and after exposure to determine total biomass and community composition. Total biomass declined with increasing doses of oil, regardless of oil type. Shifts in phytoplankton communities occurred in response to both oil types as well, although responses varied by phytoplankton type. For example, chlorophytes and cyanobacteria increased in relative abundance whereas cryptophyte abundance decreased with increasing oil concentrations. Prasinophytes, the most abundant microalga in these experiments, showed no response to oil exposure when the experiments were run in February, but a significant negative response in the March set of experiments.
These results suggest that even low concentrations of crude over short time periods could have a significant impact on phytoplankton communities. More work is needed to determine whether these impacts send ripple effects throughout the food web, but it is clear that oil spills should be prevented from reaching sensitive coastal areas if at all possible.
Source: Gilde, K. and J. L. Pinckney. 2012. Sublethal effects of crude oil on the community structure of estuarine phytoplankton. Estuaries and Coasts 35 (January 2012). DOI: 10.1007/s12237-011-9473-8.
Historically, filling and ditching tidal marshes in order to eliminate mosquito larvae habitat effectively destroyed habitat for many other species as well. Restoration projects now strive to correct some of this destruction, but the fact remains that mosquitoes, vicious biters and vectors for serious human disease, do breed in marshes. Can marsh function be restored while still minimizing mosquito populations?
A pilot project in the Wertheim National Wildlife Refuge on Long Island indicates that the answer is yes. In a marsh area where mosquito ditching had been used decades ago, integrated marsh management (IMM) was implemented, which seeks to restore marshes such that both mosquito control and habitat restoration goals are achieved. The specific management practice used in this case was to modify open marsh water management techniques in order to allow resident fish to remain on the marsh so that they could gain access to mosquito breeding locations and eat mosquito larvae. The project also filled most pre-existing ditches, while cleaning others to allow flow through of tidal waters rather than dead-ended ditches. The Long Island project team monitored two restored sites, one that had been fairly degraded before restoration and one that was relatively pristine (although previously grid-ditched), and two comparable control sites. Monitoring took place for eight years total, including three years prior to restoration.
The project appears to have been a resounding success. At the more degraded test site invasive Phragmites cover was significantly reduced after restoration, and native plant cover increased. At the more pristine site, where there had not been as much Phragmites to start, Phragmites and native plant covers remained the same. Increased abundance and diversity of key nekton species was observed post-restoration, as well as higher shorebird and waterfowl densities in the summertime. Finally, the restoration did indeed result in diminished mosquito production.
The outcomes of this project demonstrate that both mosquito control and habitat objectives can be achieved simultaneously. Another plus: the project was carried out with “in-house” expertise and labor, eliminating the need for expensive consultants and engineers.
Source: Rochlin, I., M.J. James-Pirri, S. C. Adamowicz, M. E. Dempsey, T. Iwanejko, and D. V. Ninivaggi. 2012. The effects of integrated marsh management (IMM) on salt marsh vegetation, nekton, and birds. Estuaries and Coasts 35 (January 2012). DOI: 10.1007/s12237-011-9468-5.
All submerged aquatic vegetation is not created equal, particularly when it comes to providing fish habitat. In a Prince Edward Island estuary in the Gulf of St. Lawrence system, the difference may be tied to hypoxia associated with agriculture-driven eutrophication. The high nutrient loadings there are linked to blooms of sea lettuce, which in many places has replaced formerly abundant eelgrass meadows.
Investigators examined water quality parameters and fish communities at five sites in the Stanley River estuary during April - August, 2008. All sites had generally similar temperature, salinity, dissolved oxygen, and sediment type, but three were dominated by sea lettuce and two by eelgrass. The nearshore fish community differed between types of sites in every month sampled. Overall, there were more mummichogs and fewer pipefish, sticklebacks, and silversides in the sea lettuce than in the eelgrass. In particular, the pipefish and sticklebacks were more abundant in the eelgrass during reproductive months. In August, benthic hypoxia occurred in the sea lettuce sites but not the eelgrass, leading to significantly lower fish richness and abundance at the sea lettuce sites.
The authors conclude that the significant differences observed in fish communities between the two habitat types indicate that continued eutrophication could lead to a decline in fish diversity in this system, as many common species are not adapted to thrive in the sea lettuce habitat and the accompanying low-oxygen conditions.
Source: Schein, A., S. C. Courtenay, C. S. Crane, K. L. Teather, and M. R. van den Heuvel. 2012. The role of submerged aquatic vegetation in structuring the nearshore fish community within an estuary of the southern Gulf of St. Lawrence. Estuaries and Coasts 35 (January 2012). DOI: 10.1007/s12237-011-9466-7.
What better topic for the annual H. T. Odum Synthesis Essay in the journal Estuaries and Coasts than the issue of synthesis itself? Authors Dr. Michael Kemp and Dr. Walter Boynton tackle the questions of the importance of synthesis research in coastal ecology and management, the approaches used in synthesis, and methods for encouraging more teaching and use of synthesis science. The essay is timely in this era of massive data sets and increasingly complex environmental issues that require a broad, multi-disciplinary research approach.
First the authors developed an appropriate definition of synthesis in coastal research: “the inferential process whereby new models are developed from analysis of multiple data sets to explain observed patterns across a range of time and space scales.” Five steps in conducting synthesis research are outlined (problem identification, data assembly, data integration, explanatory model development, and testing model validity) and five types of synthesis methods are outlined (comparative cross-system analysis, analysis of time series data, balance of cross-boundary fluxes, system-specific simulation modeling, and general system simulation modeling). Examples of each type are given; the authors state that it is often productive to employ several methods simultaneously.
Synthesis science is important because the scale and complexity of environmental problems affecting the coast will compel the use of multi-disciplinary approaches to help find solutions. So how do we ensure that this approach is used more often? By finding ways to teach it and support its use, the authors say. Recommendations for both are provided in the paper, including training students and young scientists to recognize patterns and anomalies, and allowing scientists to become “Renaissance people” while maintaining expertise in their chosen field. Four key challenges emerge to developing synthesis in coastal science: agreeing on what is meant by synthesis research (this publication is a step in that direction), developing an efficient system to fund and reward excellence in synthesis research, improving linkages between synthesis research and management, and developing curricula to teach synthesis science effectively.
Source: Kemp, W. M. and W. R. Boynton. 2012. Synthesis in estuarine and coastal ecological research: what is it, why is it important, and how do we teach it? Estuaries and Coasts 35 (January 2012). DOI: 10.1007/s12237-011-9464-9.