Bruce L. Boese

Desiccation is a limiting factor for eelgrass (Zostera marina L.) distribution in the intertidal zone of a northeastern Pacific (USA) estuary

Abstract Intertidal irradiance, temperature, and aerial exposure were measured for two years in intertidal Zostera marina beds located in Yaquina Bay (Newport, OR, USA). These physical data were correlated with plant growth and other metrics measured at intervals during the study. Photosynthesis vs. irradiance (P vs. I) curves were determined by PAM fluorometry on plants along an intertidal gradient, and were used to estimate saturating irradiance (Ik) and daily hours of saturating irradiance (Hsat). Mean Ik values were ∼64 μmol photons m-2 s-1 and Hsat increased with increasing tidal position. Measurements taken during the second winter showed that Hsat values in the low intertidal zone were within a critical range requiring eelgrass to use rhizome reserves to maintain carbon balance. However, plants continued to grow. Temperature differences across tidal gradients were not found to be physiologically important. These results suggested that temperature and irradiance were not limiting factors for intertidal Z. marina growth. High intertidal eelgrass, exposed to aerial conditions more frequently and for longer durations, exhibited signs of desiccation damage and appeared to have faster blade turn-over rates in spring and summer than their low intertidal neighbors. Thus, we concluded that the major factor limiting Z. marina in the upper intertidal zone was desiccation stress, which was acute and episodic rather than chronic.

Desiccation index: a measure of damage caused by adverse aerial exposure on intertidal eelgrass (Zostera marina) in an Oregon (USA) estuary

Abstract Eelgrass (Zostera marina) leaf necrosis resulting from intertidal aerial exposure is described. A desiccation index was developed and tested to quantitatively assess damage across intertidal Z. marina beds in Yaquina Bay, Newport, OR, USA. Results suggest that higher intertidal plants have more desiccation damage than those growing lower in the intertidal. This damage may partially explain why high intertidal plants tend to have shorter canopy heights as leaves tended to break at desiccation damage points.

Influences of sedimentary organic matter quality on the bioaccumulation of 4‐nonylphenol by estuarine amphipods

Nonylphenol (NP) is a moderately persistent, hydrophobic chemical with endocrine-disrupting and acute narcotic effects in aquatic biota. Concern exists about the ultimate fate of NP in aquatic ecosystems and the potential for bioaccumulation by benthic biota from the sediment with the potential for further transfer to higher trophic levels. Our goals were to determine if benthic amphipods bioaccumulate significant amounts of NP from sediment and to determine how additions of organic matter influence NP bioaccumulation by amphipods. Estuarine sediment was spiked with 14C-NP and enriched with two types of organic carbon (OC) sources of different nutritional qualities. Macrophytic algae (Ulva species) were used as a labile and nutritious OC source. Wood lignins were used as a refractory and low-nutrition OC source. Nonylphenol bioaccumulation was measured in Eohaustorius estuarius, Grandidierella japonica, and Corophium salmonis after 16 d of exposure. Nonylphenol accumulation was inversely proportional to OC quantity, but was unaffected by OC nutritional quality. Significant differences were found in the accumulation patterns between the three amphipod species. Mean biota-sediment accumulation factors ranged from 8.1 to 33.9 in E. estuarius, from 4.6 to 17.2 in G. japonica, and averaged 7.1 in male C. salmonis and 16.0 in female C. salmonis. These accumulation factors indicate that estuarine amphipods could constitute an important source of NP to higher trophic levels, such as juvenile fish.

Efficiency of uptake of hexachlorobenzene from water by the tellinid clam, Macoma nasuta

Abstract A study was undertaken to determine the efficiency with which a marine deposit-feeding clam ( Macoma nasuta ) extracted hexachlorobenzene (HCB) from water (EPW). An exposure chamber (clambox) was designed that separated the inhalant and exhalant siphons, allowing the collection of ventilated water. Seawater dosed with 14 C-labeled HCB was pumped into the inhalant chamber of the clambox. Clams were exposed to three temperatures (12, 17, 22°C) to vary weight-specific ventilation volume ( Vg ). Loss of HCB from the exhalant chamber precluded determination of EPW from the difference in HCB concentrations between the inhalant and exhalant chambers. Instead, gross EPW was calculated by dividing the HCB tissue residues by the amount of HCB to which the clam was exposed (water ventilated × the HCB concentration). Gross EPW averaged 82%. Correcting for non-gill uptake (surface sorption of HCB), gill EPW averaged 64–66%, and did not decrease with increasing Vg . In M. nasuta, Vg varied less than two-fold, which may explain the lack of a ventilation effect on EPW. HCB tissue residues were linearly related ( R 2 = 0.93) to gill exposure. The linear relationship between tissue residues and exposure supports a bioenergetics-based bioaccumulation model and indicates that factors that increase Vg , such as low oxygen concentrations, would result in more rapid uptake and a greater body burden.

Depuration kinetics of hexachlorobenzene in the clam, Macoma nasuta

1. The depuration rate constant for [14C]hexachlorobenzene (HCB) in the clam, Macoma nasuta, was determined following a short-term exposure to HCB contaminated seawater. 2. Depuration was not correlated with ventilation volume, nor did the amount of sediment ingested during depuration have a significant effect. 3. The half-life for HCB in M. nasuta was estimated to be 16 days with a bioconcentration factor of 3490 (wet weight basis).

Acute toxicity of butylbenzyl phthalate to shiner perch (Cymatogaster aggregata).

The Clean Water Act of 1971 directed the Environmental Protection Agency to establish ambient water quality criteria for several classes of elements and compounds, including phthalate esters. Multispecies acute toxicity data are required to develop these criteria. Static bioassay LC50s for butylbenzyl phthalate (BBP) for a single species of marine fish based on nominal doses range from 3 mg/L to 440 mg/L. Flow-through bioassays were used in this study of BBP with shiner perch (Cymatogaster aggregata). Using measured exposure concentrations, 96-hr LC50s averaged 0.51 mg/L. Effects on schooling behavior were found at 0.08 mg/L and coloration at 0.24 mg/L. Coupled with the behavioral changes, reduced brain levels of epinephrine found in surviving fish indicated that the mode of acute toxicity for BBP may be through its effects on the catecholamines of the central adrenergic nervous system.

The acute toxicity of butyl benzyl phthalate to the saltwater fish English sole, Parophrys vetulus.

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