HR: 0800h
AN: OS51C-0575    [Abstracts]
TI: Environmental and Biological Controls of Tidal Banding in the Common Mussel Mytilus californianus
AU: * Ford, H L
EM: hford@rohan.sdsu.edu
AF: Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1020 United States
AU: Schellenberg, S A
EM: schellenberg@geology.sdsu.edu
AF: Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1020 United States
AB: Mytilus californianus, a common intertidal mussel of the North Pacific, is often used to monitor coastal water quality via tissue incorporation of heavy metals and biotoxins, and is increasingly used to reconstruct environmental conditions (i.e. temperature, salinity, and seasonality) archived within shell carbonate. However, little is known about what governs the banded shell growth of M. californianus and accordingly, the completeness of the environmental record contained within the shell. Presumably, the most important factor determining growth is submergence (required for biomineralization and feeding), but other factors such as temperature variability, subaerial exposure, and respiration stress may also influence growth patterns.
Observations from thin sections oriented along the maximum growth axis reveal light and dark banding with diffuse purple coloration throughout the prismatic layer of the shell. Thickness of the banding oscillates from broadly to narrowly (~0.4-1.0μm) spaced light colored bands (periods of crystalline growth) separated by thin dark bands (emergence and respiration). We relate these band oscillations to 1) tidal regime and 2) mussel location within the intertidal zone. Both of these factors dictate the amount of submergence a mussel experiences and thus directly influences the growth and tidal banding.
Providing submergence primarily governs the banding oscillations found in M. californianus, we predict that 1) specimens from a low intertidal height have maximum growth during the neap tide (nearly continual submergence and feeding) and diffuse growth increments with no obvious tidal banding and 2) specimens from a high intertidal height have maximum growth during the spring tide (longest duration of submergence), with broadly spaced banding during the spring tides and narrowly spaced bands during the neap tides.
On going investigation on thin sections and acetate peels will test these growth predictions to produce a model of M. californianus growth/tidal banding based on tidal regime and intertidal position. Such model development is vital for strategic sampling of shell carbonate for stable-isotope and minor-element-ratio analyses and related seasonal reconstruction of environmental parameters such as temperature and salinity. In addition, this mussel growth model will aid in understanding the limitations of such environmental reconstructions and which intertidal height provides the most representative record.
DE: 0419 Biomineralization
DE: 0442 Estuarine and nearshore processes (4235)
DE: 4560 Surface waves and tides (1222)
DE: 4804 Benthic processes, benthos (0408)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005