A Coupled Modeling and Empirical Approach to the Study of the Life History and Physiological Ecology of Cold Seep Vestimentiferans and Communities

A coupled modeling and empirical approach to the study of the life history and

physiological ecology of cold seep vestimentiferans and communities.

Seep vestimentiferans and their symbionts are primary producers that provide complex

habitat structure in a non-toxic setting for a diverse assortment of seep-endemic and non-endemic

heterotrophic species. As such, they are arguably the most important keystone species

in widespread areas of seepage on the continental slope. Recent work has demonstrated that one

species (at least) of seep vestimentiferan is extremely long-lived and can support its autotrophic

life style with the uptake of dissolved gasses across buried portions of its body. Thus, in many

ways, the seep vestimentiferans are analogous to long-lived, ecosystem-structuring, woody plant

species in a terrestrial environment.

We will develop models to address resource acquisition and allocation, life histories, and

community productivity of cold seep vestimentiferans that will guide and focus field and

laboratory studies of cold seep vestimentiferan communities. We propose to work on the upper

Louisiana Slope of the Gulf of Mexico at a depth range of 540 to 1,000m and will include

communities on both hard substrata and sediment that are exposed to a range of sulfide

concentrations. We will use empirical studies and comparative methods to develop, test the

predictions of, and refine, Dynamic Energy Budget models, while at the same time addressing

specific hypotheses concerning vestimentiferan aggregation physiology and ecology.

Our in situ work will be guided by these mathematical models and interfaced with very

efficient and quantitative collection methods that will maximize the information gleaned from

each collection and provide material for future studies, thereby minimizing our short and long-term

impact on the communities. Growth rates of thousands of individuals will be measured and

these data used to estimate the longevity and to calculate the resources allocated to growth by

each vestimentiferan species. We will determine whether 'roots' (posterior extensions that can

be used to mine sulfide from within sediments) are a general feature of seep vestimentiferans and

whether they are environmentally induced. The models will be used to explore the relative

importance of root sulfide uptake to the sustenance of aggregations in different situations and the

implications of vestimentiferan sulfide demand on biogeochemical models of sulfide production.

To facilitate this, environmental concentrations of sulfide and diffusion distances across root

tubes and tissues will be measured, and concentrations and sulfide binding properties of the

hemoglobins in the different species will be determined. The biomass, size frequency,

distribution, and reproductive state of the vestimentiferans will be determined for intact

aggregations and collections processed so that the species richness and biomass of all associated

fauna in each collection can also be determined. This will allow us to formulate life history

models, to scale up the models of individuals to the levels of aggregations, and to model excess

production and its use by associated fauna.

Fisher has extensive experience with the Gulf of Mexico seep communities and has visited

the sites. Shea is a theoretical ecologist with experience in life-history modeling of terrestrial

and aquatic autotrophic systems. The proposed approach will significantly increase our

understanding of these widespread and productive deep-sea communities and their impact on the

surrounding deep sea, and will provide a modeling framework to focus related and future

investigations. The proposed studies will yield basic insights on the ecology, physiology and

reproductive biology of deep-sea systems in general and chemoautotrophic systems in particular.

They will also provide new theory, and tests for existing theory on the evolution of life history

strategies.