Mark G. Carls

Persistence of oiling in mussel beds after the Exxon Valdez oil spill.

Persistence and weathering of Exxon Valdez oil in intertidal mussel (Mytilus trossulus) beds in Prince William Sound (PWS) and along the Gulf of Alaska was monitored from 1992 to 1995. Beds with significant contamination included most previously oiled areas in PWS, particularly within the Knight Island group and the Kenai Peninsula. In sediments, yearly mean concentrations of total petroleum hydrocarbons ranged from < 60 micrograms/g in reference beds to 62,258 micrograms/g wet wt., or approximately 0 to 523 micrograms/g dry wt. total polynuclear aromatic hydrocarbons (TPAHs). In mussels, mean TPAH concentrations ranged up to 8.1 micrograms/g dry wt. Hydrocarbon concentrations declined significantly with time in some, but not all mussels and sediments, and should reach background levels within three decades of the spill in most beds. In 1995, mean hydrocarbon concentration was greater than twice background concentration in sediments from 27 of 34 sites, and in mussels from 18 of 31 sites.

Effects of fluctuating temperature on mortality, stress, and energy reserves of juvenile coho salmon

Abstract The effects of fluctuating diel temperature cycles on survival, growth, plasma cortisol and glucose concentrations, liver weight, and liver glycogen of juvenile coho salmon Oncorhynchus kisutch were determined. Temperature cycles (10–13°, 9–15°, 8–17°, and 6.5–20°C) were selected to simulate observed temperatures in clear-cuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. LT50s (peak temperature within a cycle producing 50% mortality) were 28°C for age-0 fish (350 mg) and 26°C for age-II fish (22-g presmolts). Cyclic temperatures for 40 d, averaging 11°C daily, did not influence growth of age-0 fish on any food ration as compared to controls held at a constant 11°C. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5–20°C cycle but not different in fish in 10–13° and 9–15°C cycles or a constant 11°C. These elevated concentrations may be indicators of long-term stress. Plasma corti...

A Perspective on the Toxicity of Petrogenic PAHs to Developing Fish Embryos Related to Environmental Chemistry

ABSTRACT Numerous studies demonstrate polynuclear aromatic hydrocarbons (PAHs) dissolved from weathered crude oil adversely affect fish embryos at 0.5 to 23 μg/l. This conclusion has been challenged by studies that claim (1) much lower toxicity of weathered aqueous PAHs; (2) direct contact with dispersed oil droplets plays a significant role or is required for toxicity; (3) that uncontrolled factors (oxygen, ammonia, and sulfides) contribute substantively to toxicity; (4) polar compounds produced by microbial metabolism are the major cause of observed toxicity; and (5) that based on equilibrium models and toxic potential, water contaminated with weathered oil cannot be more toxic per unit mass than effluent contaminated with fresh oil. In contrast, several studies demonstrate high toxicity of weathered oil; shifts in PAH composition were consistent with dissolution (not particle ablation), embryos accumulated dissolved PAHs at low concentrations and were damaged, and assumed confounding factors were inconsequential. Consistent with previous empirical observations of mortality and weathering, temporal shifts in PAH composition (oil weathering) indicate that PAHs dissolved in water should (and do) become more toxic per unit mass with weathering because high molecular weight PAHs are more persistent and toxic than the more abundant low molecular weight PAHs in whole oil.

Identification and First Documentation of Larval Rockfishes in Southeast Alaskan Waters Was Possible Using Mitochondrial Markers but Not Pigmentation Patterns

Abstract More than 30 species of rockfish (genus Sebastes) occur in Alaskan waters, but their larvae generally cannot be identified by morphology. Consequently, knowledge of life histories is incomplete for this commercially and ecologically valuable taxon, and the locations and habitats of the larvae of specific species have not been determined. We used mitochondrial DNA markers, which now can delineate most Alaskan rockfishes, to identify larvae collected in ichthyoplankton surveys conducted in Southeast Alaskan waters. We report the occurrence of 15 species or species groups. Sebastes zacentrus (sharpchin rockfish), S. proriger (redstripe rockfish), and members of the indistinguishable group S. variegatus (harlequin rockfish)−S. wilsoni (pygmy rockfish)−S. emphaeus (Puget Sound rockfish) were observed every year and in most collections in Chatham Strait and along western Prince of Wales Island. Sebastes zacentrus was abundant only in Chatham Strait; S. auriculatus (brown rockfish) and S. elongatus (gre...

Sensitivity differences between eggs and larvae of Walleye pollock (Theragra chalcogramma) to hydrocarbons

Abstract Exposure of embryonic and larval walleye pollock ( Theragra chalcogramma ) to the water-soluble fractions (WSF) of Cook Inlet crude oil during embryonic development caused mortality and a variety of morphological abnormalities. Median WSF concentrations (1·8 ppm) which caused mortality after hatch did not differ significantly from those causing morphological abnormalities (1·6 ppm). Pollock larvae exposed to WSF did not develop abnormalities, but swimming and survival were significantly affected within 4 h of exposure. The LC 50 for larvae dropped from 1·9 ppm on day 4 to 0·9 ppm on day 10. The tissue of developing pollock larvae bioaccumulated significantly more dissolved toluene and naphthalene than those of embryos. Consequently, when exposed to equal concentrations of WSF, larval tissues are exposed to much higher hydrocarbon concentrations than embryonic tissues. On the basis of internal tissue concentrations, larvae were less sensitive than eggs, but the opposite conclusion is reached if external (WSF) concentrations are used for estimation of sensitivity.

Toxic contributions of specific drilling mud components to larval shrimp and crabs

Abstract We investigated the toxicities of six drilling muds, toxicities of mud fractions (supernatants and suspensions) and the toxicities of common mud components—barite and bentonite (particulates) and ferrochrome lignosulfonate (soluble)—to the stage I larvae of six species of shrimp and crab. The drilling muds we tested were not very toxic to these larvae: LC50s for supernatants ranged from 0·6 to 82% (vol/vol). Shrimp larvae were slightly more sensitive than crab larvae. Drilling muds were not rapidly toxic, in contrast to toxicants such as the water-soluble fractions of oil. Supernatants, prepared by centrifuging whole muds, were mildly toxic. Suspensions were more toxic than supernatants and toxicity was greatest when particulates remained suspended: for example, used Cook Inlet mud suspensions were about seven times more toxic than supernatants. The toxicity of used Cook Inlet mud was therefore primarily due to suspended solids (88%) rather than chemical toxicity: ferrochrome lignosulfonate was relatively toxic alone, but accounted for only about 6% of the toxicity of used Cook Inlet mud suspensions. Contributions of particulates to mud toxicities varied considerably. Barite and bentonite were not very toxic when tested alone. The toxicity of one mud was caused by its high alkalinity.

Mixed function oxygenase induction in pre- and post-spawn herring (Clupea pallasi) by petroleum hydrocarbons

We compared the uptake of water-accommodated fractions of Alaska North Slope crude oil in pre- and post-spawn herring (Clupea pallasi) and the resulting induction of mixed function oxygenase activity. Both groups of herring accumulated significant quantities of polycyclic aromatic hydrocarbons in muscle tissue. Pre-spawn herring accumulated higher concentrations of hydrocarbons and retained them longer. Induction of mixed function oxygenase activity in pre-spawn fish was one-third to one-half that in post-spawn fish. Inability of pre-spawn herring to induce mixed function oxygenases at as high a level as post-spawn fish may explain higher tissue concentrations and retention of hydrocarbons in the pre-spawn animals.

Observer Classification of Live, Mechanically Damaged, and Dead Pink Salmon Eggs

Abstract The susceptibility of pink salmon Oncorhynchus gorbuscha eggs to mechanical damage (shock) was studied to test the ability of observers to discriminate among live, dead, and damaged eggs. In a series of six laboratory trials, the mean error rate in discrimination did not exceed 12% and was 3.5% or less in four of six trials. The most common error was misclassification of damaged eggs as live (≤9 ± 1% (mean ± SE)), an error that is irrelevant in field studies designed to determine the natural death rate. The second most common error was damaged eggs classified as dead (≤4.6 ± 1%) when observation times were 60 min or less; this was reduced to less than 0.5% when observations were limited to 12 min or less. Inexperienced observers were easily trained (within 1 h) to classify eggs. To accurately describe natural systems before sample disturbance, damaged and dead egg categories should not be combined when reporting data.