Oiled Sea Otter Rehabilitation Course

Blood Analysis and Pathology

Detailed postmortem examinations will greatly augment current deficiencies in our understanding of the pathophysiological effects of oil. To ensure high standards during specimen collection, all fresh carcasses should be examined under laboratory conditions whenever possible. Macroscopic and microscopic findings should be correlated with the clinical history of the animals. Serial blood samples from oiled and non-oiled animals yield potentially invaluable data that can be used to direct treatments and subsequently to document the nature of the impact.

Blood should be collected into three types of sterile containers:

  1. 15% EDTA anticoagulant for hematology,
  2. potassium oxalate anticoagulant for measurement of petroleum hydrocarbons, and
  3. no anticoagulant for serum biochemical analysis. A full profile for routine hematology and plasma biochemistry should be run for all samples. Constituents that are sensitive to stress are particularly important. Cortisol, serum iron and erythrocyte sedimentation rate were useful indicators of stress in sea otters (Williams and Davis, 1990). However, individual variation in baseline values may mask some of the stress-related changes. A large sample of control and oiled animals may be needed to establish differences between the groups. In phocid seals, aldosterone and sodium are particularly useful measures (St. Aubin and Geraci, 1986).

Oiled fur seal pups showed a typical stress leukogram. Marked leukocytosis, due to a neutrophilia, with a concomitant lymphopenia and eosinopenia, was noted in pups at the time of oiling; the leukogram returned to normal ranges within two months (Gales, 1991). No other hematological or serum biochemical change signalled systemic toxicosis or organ dysfunction following oil exposure (Gales, 1991). This contrasts markedly with the results for sea otters (see Chapter 5 and Appendix 3 Download PDF).

Petroleum hydrocarbon levels in blood can indicate the degree and route of absorption. Straight chain hydrocarbons are absorbed through the gut, whereas aromatic compounds are absorbed primarily by inhalation, and to a much lesser extent through the skin. For most marine mammals, there is little background data on circulating levels of petroleum hydrocarbons. Interpretation of any findings after oil exposure rests on the assumption that such compounds are normally undetectable. Observations on the dynamics of petroleum hydrocarbon levels in blood will greatly assist future attempts to understand the significance of such data.