The study of marine organisms can provide insight of exceptional clarity to past, current and future climatic, geological, and biological conditions. The use of transmission electron microscopy (TEM), scanning electron microscopy (SEM), and light microscopy are essential in advancing our ability to detect and assess the effects of regional and global environmental change on marine invertebrates. Coccolithophorids are small (~5 μm) unicellular mainly marine algae, covered with calcified plates of diverse and intricate morphologies known as coccoliths. They can be an important component of the phytoplankton, and are a major producer of calcium carbonate in the world ocean. TEM studies have shown that coccoliths are produced intracellularly within vesicles, are extruded, and adhere to the cell surface (Fig. 1). Variability in Ca, Mg and Sr in growth media of cultured representatives have effects on cell ultrastructure and coccolith mineralogy, facilitating interpretation of the effects of variability in ocean ionic composition over geologic time . Ostracods are small laterally compressed crustaceans, usually < 1 mm in length, protected by a bivalve-like, calcareous carapace. Marine ostracods are typically benthic organisms, are commonly found as microfossils, and have a long, well-documented fossil record particularly valuable in paleoreconstruction studies. SEM and TEM studies of ostracods include the morphology of sieve pores and carapace nodes demonstrating that ostracods may be sensitive salinity indicators (Fig. 2). This data coupled with community analyses may be used to reconstruct natural rainfall patterns and anthropogenic effects such as water management practices and documented anthropogenic usage . Coral reefs are extensive biomineralized structures and are dominant features of tropical coastlines worldwide, covering ~15% of seabed < 30 m deep. They have a significant oceanic geochemical impact, and the specific ratios of their skeletal chemistry provide excellent chronological records of environmental conditions. Histologic techniques are used to assess overall tissue and cellular condition, and extending histological observations to the ultrastructural level enables detection of initial changes and variability in coral tissue, skeleton and symbiotic dinoflagellate cellular structure and morphology resulting from anthropogenic environmental factors and disease (Fig. 3) . Microscopic study and analysis of marine invertebrates can provide valuable data on organismal response to changes in environmental parameters such as seawater composition, temperature, CO2 partial pressure and nutrification. In turn, this data provides valuable information useful for establishment of “proxies” in prediction and management of the ever-changing marine environment.
Available at: http://works.bepress.com/patricia-blackwelder/21/