Reprint Series No. 16

SEA SURFACE FILMS: DEPOSITION AND TOXICITY IN INTERTIDAL HABITATS

William Wood Gardiner

1992

Bibliographic Citation
Gardiner, William Wood. 1992. Sea surface films: deposition and toxicity in intertidal habitats. M.S. Thesis, Western Washington University, Bellingham, Washington. 72 pp. Padilla Bay National Estuarine Research Reserve Reprint Series No. 16.

Abstract
Sea surface films are a concentration point for organic and inorganic compounds, bacteria, phytoneuston, zooneuston, and detritus. Atmospheric, terrigenous, and marine anthropogenic contaminants are also enriched at the surface, causing lethal and sub-lethal toxic effects in marine vertebrates and invertebrates. In coastal regions, wind, waves, and surface currents drive surface film shoreward, making them available for littoral interaction. Beaching of drift cards and sea foam indicates the potential for surface film deposition, or stranding, as the tide recedes. The objectives of this study were to demonstrate sea surface film deposition during tidal ebb and to determine the relative toxicities of these deposits in rural, semi-rural, and urban embayments.

A modified Garrett screen sampler was designed to collect surface film deposits. Stranding was demonstrated in a series of five in situ labeling experiments using surface active Lycopodium spores. Mean spore recoveries in surface film (SL) samples (6,896 spores/ml) and surface deposit (SD) samples (12,711 spores/ml) were significantly higher than those of bulkwater samples (0 spores/ml). A mean SD:SL spore density ratio of 3.7 suggested a magnification effect during deposition. This effect may have been a natural concentration process as surface film materials strand during the tidal ebb.

Surface deposit, surface film, and bulkwater toxicity was evaluated for Discovery, Padilla, and Commencement Bays using three echinoderm (Dendraster excentricus) bioassays. The 48-h development test measured percent mortality (M) and percent abnormality (A). The sperm cell test (SCT) assayed sperm viability (S) and a cytogenetic bioassay measured alterations in embryonic mitosis. Commencement Bay surface deposits produced significantly higher rates of mortality, larval deformity, and SCT response (M-37.0%; A-30.6 %; S-39.9%) than deposit samples from either Padilla (M-12.8%; A-10.0%; S-5.4%) or Discovery Bay (M-2.2%; A-3.1%; S-8.7%). Larvae incubated in Padilla Bay surface deposits had significantly higher mortalities than those of Discovery Bay. Significant increases in percent anaphase aberrations were detected in larvae incubated in both Commencement (36.2% abnormal anaphase) and Padilla Bay (8.0% abnormal anaphase) surface deposits, while Commencement Bay surface deposit samples had a significantly reduced mitotic index (8.0 mitoses/embryo).

Larvae incubated in Commencement Bay surface films had significantly higher rates of mortality and abnormality than larvae in either Padilla or Discovery Bay surface film samples. Bulkwater responses in all tests were considerably lower than both surface film and surface deposit responses for all three embayments.

The spore labeling experiments demonstrated that free floating surface films are deposited onto intertidal substrates during tidal ebb. In coastal regions, such as Puget Sound, this stranding of organically enriched surface films represents a potential transfer of marine surface materials into littoral habitats. Dendraster excentricus bioassays indicated that contaminated surface deposits can produce developmental, reproductive, and mutagenic effects. A conceptual model based on surface current, wind, demographic, and drift card data predicted that Puget Sound shorelines which are downwind or downcurrent from contaminant sources are especially at risk from these effects.