238-11 Using Ammonia parkinsonia Morphology as a Bioindicator for Environmental Stress in Matagorda Bay

Session: Recent Advances and New Voices in Marine and Coastal Geoscience

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Foraminiferal assemblages are frequently used for environmental health monitoring and certain species of foraminifera are highly sensitive to temperature changes, salinity shifts, and pollution. Although benthic foraminiferal assemblages are generally used for monitoring estuarine health, assemblage variation can be subtle in these low-diversity assemblages. In situations such as this, variation in body size and reproductive mode within individual species can provide clearer insight into environmental stress.

Body size in benthic foraminifera has also been shown to reflect environmental conditions such as salinity, temperature, and can respond to anthropogenic impacts. Ammonia spp. is an abundant genus in estuarine environments and relative abundances of different Ammonia species are used as bioindicators for estuarine health. This study investigates whether morphological changes in Ammonia parkinsonia reflect the varying environmental impacts on four sites within the Matagorda Bay System: Caranchua Bay, Cox Bay, East Matagorda Bay, and Tres Palacios Bay. Cox Bay, which is located near the Alocoa Point Comfort Superfund site, has a history of industrial mercury contamination. Caranchua and Tres Palacios Bay are each influenced by agricultural runoff. In contrast, East Matagorda Bay serves as a control site with minimal anthropogenic impact.

Cox Bay shows a decline in Ammonia parkinsonia body size in sediments deposited after 1970 during intervals of elevated mercury concentrations. However, near the top portion of the core after remediation efforts began, body size increased but did not reach pre-impact sizes. Caranchua Bay and Tres Palacios show a similar decline in body size beginning at ~1980-1990 and persisting to the present. Lastly, East Matagorda Bay shows relatively stable body size since the late 1800s, consistent with its history of lower human impact. Thus, Ammonia parkinsoniana shows potential as a biomonitoring tool for tracking contamination and recovery in estuarine systems.  Ongoing work is examining whether reproductive mode, determined by the size of the initial chamber of the shell, is also associated with these environmental changes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10067

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