International Research Fellowship Program: Vulnerability and Resilience of Sponge Populations and their Bacterial Symbionts to Climate Change and Anthropogenic Disturbances

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0853089ErwinThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Patrick M. Erwin to work with Dr. Xavier Turon at the Centre of Advanced Studies of Blanes and at the Spanish Research Council in Blanes, Spain.The short-term vulnerability and long-term resilience of marine organisms to anthropogenic stressors will dictate the future of aquatic ecosystems and will, in turn, have a large impact on humankind's interactions with the sea. The negative consequences of human activities affect nearly all marine organisms; however, sessile, filter-feeding invertebrates inhabiting coastal environments are especially susceptible, due to adult immobility, concentrated exposure to waterborne pollutants and proximity to dense human populations. Sponges are ancient, filter-feeding organisms that thrive in a variety of marine environments and are essential to the healthy functioning of marine ecosystems. Sponge-microbial associations represent unique symbioses between a basal and primitive multi-cellular animal group and ancient bacterial lineages that appear to have co-evolved and endured a wide range of environmental conditions. Changes in the composition of microbial symbionts are an early signal of the disruption of the relationships within the sponge holobiont, with the loss of beneficial bacteria and proliferation of infectious and parasitic microbes. The critical importance of associated microbial communities to host sponge health offers an ideal system to study the impact of natural and anthropogenic stressors on host-symbiont stability and the consequences of disrupting bacterial symbiont communities on host sponge fitness.Assessing the vulnerability and resilience of individual organisms and entire ecosystems to increasing pollution and climate shifts involves monitoring the effects of both lethal and sub-lethal levels. The effects of lethal pollution are studied at the community and species level, documenting shifts in community composition and tracking bioindicator species. These responses are ultimate and are evidenced only after prolonged exposure. In contrast, sub-lethal responses to pollution and climate change are studied at the cellular and molecular level because small doses of pollutants or temperature changes may affect the physiological functions and behavior of organisms without killing them. Thus, changes at the molecular level occur before those that can be detected by classical monitoring and bioassays so that molecular biomarkers can be considered as early warning systems for sub-lethal effects of contamination and stress.The current study is a multi-scale research project examining the ecological (growth and survival), physiological (host-symbiont interactions) and cellular (gene expression) responses of Mediterranean sponges and their symbiotic microflora to natural and anthropogenic stressors. The field component of the study involves monitoring undisturbed and experimentally shaded sponges (Ircinia fasciculata and I. variabilis) over 1.5 years to assess seasonal variability in gene expression of the hsp70 stress protein, symbiont photosynthetic activity and symbiont diversity and to determine the role of autotrophic nutrition from symbionts in host sponge growth and stress status. The laboratory component of the study involves exposing the same sponge species to heavy metals, pesticides and increased seawater temperatures under controlled aquaria conditions to assess the potential effects of pollutants and climate change on the community structure of microbial symbionts and the cellular stress responses of host sponges. In the face of increasing human populations and unprecedented environmental conditions resulting from global climate change, addressing the vulnerability and resilience of organisms to new disturbance regimes is critical to the preservation of current ecosystems and the forecasting of future anthropogenic impacts on natural systems.