Michael S. Stekoll

Sublethal exposure to crude oil during embryonic development alters cardiac morphology and reduces aerobic capacity in adult fish

Exposure to high concentrations of crude oil produces a lethal syndrome of heart failure in fish embryos. Mortality is caused by cardiotoxic polycyclic aromatic hydrocarbons (PAHs), ubiquitous components of petroleum. Here, we show that transient embryonic exposure to very low concentrations of oil causes toxicity that is sublethal, delayed, and not counteracted by the protective effects of cytochrome P450 induction. Nearly a year after embryonic oil exposure, adult zebrafish showed subtle changes in heart shape and a significant reduction in swimming performance, indicative of reduced cardiac output. These delayed physiological impacts on cardiovascular performance at later life stages provide a potential mechanism linking reduced individual survival to population-level ecosystem responses of fish species to chronic, low-level oil pollution.

Sublethal effects of chronic oil exposure on the intertidal clam Macoma balthica

When exposed to Prudhoe Bay crude oil in flowing seawater for 180 days, the small intertidal clam Macoma balthica showed behavioral, physical, physiological and biochemical changes. At a high concentration of oil in seawater (3.0 mg l-1) burrowing rate decreased, respiration rate increased, growth was inhibited, and very high mortalities resulted. The lowest concentration of oil in seawater (0.03 mg l-1) inhibited growth and caused reabsorption of gametes. One group of adverse oil effects which was related to sluggishness and disorientation of the clams appeared after a week of exposure to oil; another group related to a negative energy balance was not observed until 60 days. We conclude that chronic exposure of M. balthica to oil-in-seawater concentrations even as low as 0.03 mg l-1 will, in time, lead to population decreases.

Accumulation, fractionation and release of oil by the intertidal clam Macoma balthica

The bivalve mollusc Macoma balthica accumulated hydrocarbons during 180 days of continuous exposure to Prudhoe Bay crude oil in seawater dispersions with nominal concentrations of 0.03, 0.3 and 3.0 mg l-1. The molluscs ability to concentrate oil from seawater increased with decreasing oil-in-water concentration. Decreases in oil burden began after 30 to 120 days (depending on the oil concentration) and continued for at least 60 days after exposure to oil ceased. Aliphatic and aromatic hydrocarbons were fractionated in markedly different ways by the bivalve. Branched and cyclic aliphatics in the molecular weight-range dodecane through hexadecane were preferentially retained over straightchain and their higher homologs. Larger and more substituted aromatic compounds were selectively concentrated. There appeared to be no selective concentration of aromatic sulphur compounds.

Eelgrass (Zostera marina L.) in Prince William Sound, Alaska: Effects of the Exxon Valdez oil spill

Possible injury to, and recovery of, populations of eelgrass, Zostera marina L., in Prince William Sound were assessed following the Exxon Valdez oil spill by comparing populations at oiled vs reference sites between 1990 and 1995. Eelgrass beds in !heavily oiled bays were exposed to moderate concentrations of hydrocarbons. In 1990, a year after the spill, concentrations of total polycyclic aromatic hydrocarbons averaged nearly 4000 ng g-1 dry weight of sediment at oiled sites compared to less than 700 ng g-1 at reference sites. Injuries to eelgrass, if any, appeared to be slight and did not persist for more than a year after the spill. There were possible effects on the average density of shoots and flowering shoots, as these were 24 and 62% lower at oiled than at reference sites in 1990 (p < 0.10 for both). However, there were no differences between oiled and reference sites with respect to eelgrass biomass, seed density, seed germination or the incidence of normal mitosis in seedlings, and there were no signs of the elimiwation of eelgrass beds. Populations recovered from possible injuries by 1991, as there was a sharp decline in hydrocarbon concentrations and there were no differences in shoot or flowering shoot densities between oiled and reference sites in 1990 or subsequent years.

Hepatic aryl hydrocarbon hydroxylase activities in coho salmon (Oncorhynchus Kisutch) exposed to petroleum hydrocarbons

Coho salmon exposed to the water soluble fraction (WSF) of Cook Inlet crude oil for a maximum of 30 days showed a greater than three-fold increase in hepatic aryl hydrocarbon hydroxylase activity. The initial increase in enzyme activity appeared between 2 and 5 days of exposure and increased as a function of increased exposure time. Persistence of the induced enzyme activity was dependent on the length and the concentration of WSF exposure. Handling stress had no effect on the AHH activity, but starvation caused a decrease in the activity.

A remote sensing approach to estimating harvestable kelp biomass

Regulations of the Alaska Department of Fish and Game require that all fisheries in the state have a harvest management plan. In southeast Alaska two species of floating kelps, Nereocystis luetkeana and Alaria fistulosa, have been commercially harvested since 1992 for use as agrochemicals by the Alaska Kelp Company. However, there is currently no harvest management plan for this fishery. The lack of a formalized management plan is one factor that has kept the kelp industry from expanding in the state. We have employed an aerial digital multispectral imaging system (DMSC) calibrated with ground truthing for performing such an assessment. The system can be flown at varying altitudes to achieve spatial resolutions ranging from 0.5 to 2 m. Rapid ground truthing techniques were developed using morphometric measurements to predict biomass. Analysis of the DMSC imagery showed that good correlations could be developed between the multispectral imagery and kelp biomass estimates collected at the ground-truth sites. Repeatable estimates of kelp bed area derived from the multispectral imagery could be made at varying tidal levels. However, broad scale maps of kelp biomass suitable for estimating harvest rates could not be made at different tide levels. Multispectral imagery suitable for this purpose must be collected at a standard tidal level.

Recolonization and restoration of upper intertidal Fucus gardneri (Fucales, Phaeophyta) following the Exxon Valdez oil spill

The Exxon Valdez oil spill in March 1989 and subsequent cleanup caused injury to intertidal Fucus gardneri populations especially in the upper intertidal. A survey in 1994 in Prince William Sound, Alaska showed that the upper boundary of Fucus populations at oiled sites was still an average of 0.4 m lower than the upper boundary at unoiled sites. Restoration of severely damaged Fucus populations was started on a small-scale at a heavily oiled rocky site in Herring Bay, Prince William Sound. Experiments employed mats of biodegradable erosion control fabric to act as a substratum for Fucus germlings and to protect germlings from heat and desiccation stress. A series of plots was covered with mats made from a resilient coconut-fiber fabric in June 1993. Half of the mats were inoculated with Fucus zygotes. A series of uncovered control plots was also monitored. There was no enhancement of Fucus recruitment on the rock surfaces under the mats. Dense populations of Fucus developed on the surface of all of the mats by the summer of 1994. The natural rock surfaces in the control plots, both inoculated and not, were barren of macroscopic algal cover. By September 1994, the juvenile thalli on the mats were approximately 2 cm in length. Inoculating the mats had an effect only in the upper region of the intertidal. It is expected that the thalli will become fertile during the 1995 season. These thalli may serve as a source of embryos to enhance the recovery of new Fucus populations in this high intertidal area.

Colonization of mine tailings by marine invertebrates.

An experiment was conducted to determine if a tailings substrate would inhibit recolonization of benthic macrofauna upon closure of a submarine tailings disposal (STD) operation. Trays of defaunated marine sediment, serving as a reference, and trays of tailings from a proposed gold mine were placed at 21 m depth on the ocean floor to allow colonization via settlement from the water column. Trays of reference sediment and tailings, and cores of ambient sediment were collected 9, 17, and 22 months after tray placement. Probable tray effects, which were desirable given the objectives of this study, precluded direct comparison of ecological succession in the tray sediments to the ambient assemblage. The ambient macrofauna assemblage was distinguishable from the reference sediment and tailings assemblages throughout the experiment and displayed more pronounced seasonality. Differences between the reference sediment and tailings assemblages were generally insignificant, including total abundance, total biomass, number of taxa, average size of individuals, numerically dominant taxa, abundance by ecological guilds, and overall community composition. Upon cessation of STD, recolonization of a benthic macrofauna community should not be inhibited by the presence of these tailings as a benthic substrate.

Porphyra cultivation in Alaska: conchocelis growth of three indigenous species

Experiments were performed to determine the range and optima of environmental conditions under which indigenous species of Alaskan Porphyra can grow. Growth of the conchocelis phase of Porphyra abbottae, P. torta and P. pseudolinearis was measured, when cultured in enriched media, under long days (16 h light) and varying conditions of irradiance (20, 40, 80 and 160 μmol photons m−2 s−1), temperature (7, 11, 15 and 19 °C) and salinity (5, 10, 20, 30 and 40 ‱). Optimal growth (7.6% increase in volume day−1) of P abbottae occurred at 11 °C, 80 μmol photons m−2 s−1 and 30 ‱. Porphyra torta grew best (6.5% day−1) at 15 °C, 80 /xmol photons m−2 s−1 and 30 ‱. Porphyra pseudolinearis generally had higher growth rates than the other two species with optimal growth (8.8% day−1) occurring at 7 °C, 160 μmol photons m−2 s−1 and 30 ‱. For all three species salinity between 20 and 40 ‱ had little effect on growth, but there was virtually no growth at salinity of 10 ‱ and below. Irradiances between 20 and 160 μmol photons m−2 s−1 generally had little effect on growth rates. However, growth of P. abbottae increased with irradiance at 7 °C but was inhibited at irradiances over 40 μmol photons m−2 s−1 at 15 °C and higher. Porphyra torta also showed growth inhibition at 15 °C and higher irradiances. Porphyra pseudolinearis appeared to be the most robust species with respect to tolerance to extremes of salinity and irradiance.

Response of the Dominant Alga Fucus gardneri (Silva) (Phaeophyceae) to the Exxon Valdez Oil Spill and Clean-up

The Coastal Habitat Injury Assessment Study was initiated to assess injury to and recovery of intertidal habitats aAected by the Exxon Valdez oil spill, 1989, and subsequent clean-up. The spill area was divided into three major regions: Prince William Sound (PWS), Cook Inlet-Kenai (CIK) and Kodiak‐Alaska Peninsula (KAP) and distinct habitat types within the area. The dominant intertidal macrophyte, Fucus gardneri, was impacted over the entire area of the spill, although observed diAerences varied across regions, habitats, and tidal heights. Generally F. gardneri biomass and percent cover were reduced in most habitats. However, at the low intertidal in CIK sheltered rocky habitat, the F. gardneri population was enhanced at the expense of annuals. Thalli of F. gardneri at oiled sites were not as reproductively competent as those at reference sites. Population structures were also altered. A greater proportion of adult F. gardneri thalli had attached epiphytes in oiled sites. Additional data collected during 1992‐1994, indicate varying rates of recovery for F. gardneri populations. ” 2000 Elsevier Science Ltd. All rights reserved.