Effects of anthropogenic eutrophication on the ecosystem services provided by shoalgrass

End Date: 01/31/06


It is well known that seagrass meadows provide a series of important services to coastal ecosystems, such as offering shelter to many juveniles, providing food for many local and distant organisms, and being important reservoirs of organic matter. Surprisingly, all those contentions mainly proceed from a few well-studied species, but the services provided by many wide-spread species, such as shoalgrass (Halodule wrightii), are poorly known.

To contribute towards this gap, we have been conducting research over the last year with MASGC Program Development funds (#R/CEH-10-PD). Our results are encouraging and allow us to hypothesize that shoalgrass meadows are important habitats and food grounds for many organisms, and significant organic reservoirs in coastal ecosystems of the Gulf of Mexico. Those results however, are preliminary since they are based on limited research. Our first research objective is to confirm these important services of shoalgrass meadows.

Our second research objective stems from an imperative need caused by the increasing occupation of the coastal environment by human populations: the understanding of how anthropogenic eutrophication affects the ecosystem services of shoalgrass meadows. Anthropogenic eutrophication often causes the build-up of algal biomass in seagrass meadows and, through a series of deleterious effects (e.g. light limitation), a resulting decrease in seagrass abundance. We hypothesize that algal/shoalgrass assemblages caused by anthropogenic eutrophication will offer similar services to those offered by pristine shoalgrass meadows if the algal build-up is not conducive to frequent and/or intense hypoxia. Our rationale is that, if oxygen concentrations do not drop to sub-lethal levels, large algal accumulations would also offer numerous refuge and food possibilities for organisms, and store large pools of organic matter, thereby compensating for the negative effects of shoalgrass decline on those services.

To accomplish the two research objectives, we will compare a number of variables indicative of the services targeted between control and fertilized plots in three meadows seasonally over two years. The fertilization technique we will use has proven operative for generating macroalgal build-ups and associated seagrass decline. Overall, the experimental plan, by including substantially increased effort in the number of variables and meadows examined, a higher sampling frequency, and a longer duration in relation to our prior MASGC Program Development project, will allow us to derive a robust test of our hypotheses.

The results will be valuable for managers interested in policies for the sustainable development and exploitation of our coastal resources. Hence, to best disseminate and apply our results to real-world management problems, we will organize a workshop with local managers and renowned scientist with experience in eutrophication at the end of the project. The workshop will be organized in collaboration with the Coastal Policy Center at the Dauphin Island Sea Lab, which has much experience in applying scientific results to solving management questions.

Our third objective is educational. We will contribute to conveying a correct perception and attitude towards the problem of eutrophication to our society by targeting high-school teachers. We believe this is an efficient method because high school teachers interact with many students, who in turn represent the future wave of professionals and can do much with their actions and decisions, to curb the extent of the problem. Each summer during the two years of the project, we will organize a two-week long course on eutrophication for high school teachers.

We will also provide the teachers with a state-certified curriculum guide on eutrophication so they can transfer all the relevant knowledge and experiences to their students in an efficient and practical (i.e. generating credit-hours towards graduation) way. The course will be held at the Dauphin Island Sea Lab and organized and co-taught in collaboration with the staff of environmental educators at the Discovery Hall Programs at the Sea Lab, which is one of the most-renowned programs for environmental education in the nation.


During the second year, we will continue the work exactly in the same way as in the first year. This is so because we will need to continue our experimental approach over two years to obtain robust conclusions for our hypotheses. Hence, our objectives for the second year remain unaltered, namely

  1. to confirm the important services provided by shoalgrass meadows to coastal ecosystems of the Gulf of Mexico that our preliminary results obtained with MASGC Program Development funds suggest
  2. to examine the effects of algal accumulation and shoalgrass decline resulting from anthropogenic eutrophication on those services
  3. to contribute to the education of our society on the consequences of and solutions to anthropogenic eutrophication


The same methodology also applies to Yr. 2. Namely, to accomplish objectives 1 and 2, we will compare control and fertilized plots in three shoalgrass meadows seasonally over two years. A number of measurements indicative of important services provided by the meadows, such as the extent of refuge and food offered to organisms and the storage of organic matter, will be taken and compared between control and fertilized plots. To accomplish objective 3, we will organize a two-week course on eutrophication for high school teachers and provide them with a curriculum guide on eutrophication to help them disseminate the experience acquired back in their home high schools. 


The rationale also remains the same. Anthropogenic eutrophication of our coastal resources is a world-wide problem. Hence, we need to elucidate how the problem can affect the services provided by important coastal resources such as seagrass meadows. That information is essential for a correct management of the use and development of coastal ecosytems.