Bottlenose Dolphins as Marine Ecosystem Sentinels: Developing a Health Monitoring System

Abstract

Bottlenose dolphins (Tursiops truncatus), as long-lived, long-term residents of bays, sounds, and estuaries, can serve as important sentinels of the health of coastal marine ecosystems. As top-level predators on a wide variety of fishes and squids, they concentrate contaminants through bioaccumulation and integrate broadly across the ecosystem in terms of exposure to environmental impacts. A series of recent large-scale bottlenose dolphin mortality events prompted an effort to develop a proactive approach to evaluating risks by monitoring living dolphin populations rather than waiting for large numbers of carcasses to wash up on the beach. A team of marine mammal veterinarians and biologists worked together to develop an objective, quantitative, replicable means of scoring the health of dolphins, based on comparison of 19 clinically diagnostic blood parameters to normal baseline values. Though the scoring system appears to roughly reflect dolphin health, its general applicability is hampered by interlaboratory variability, a lack of independence between some of the variables, and the possible effects of weighting variables. High score variance seems to indicate that the approach may lack the sensitivity to identify trends over time at the population level. Potential solutions to this problem include adding or replacing health parameters, incorporating only the most sensitive measures, and supplementing these with additional measures of health, body condition, contaminant loads, or biomarkers of contaminants or their effects that can also be replicated from site to site. Other quantitative approaches are also being explored.

Sequence Analysis of MHC Class II Genes in Cetaceans

“…Still of concern is the potential transmission of novel pathogens into populations of T. aduncus not equipped with the specific immunogenetic repertoire necessary for an effective immune response. Dolphin health and population status reflect the effects of natural and anthropogenic stressors on the species (Wells et al, 2004). Monitoring the health of T. aduncus could serve as not only sentinels of the health and status of lower trophic levels in the marine system, but also indicators and warning of impacts on human as more humans inhabit coastal regions.…”

Predicting the effects of human developments on individual dolphins to understand potential long-term population consequences

“…There are stable inshore populations of cetaceans where even more detailed data are available, for example the population of bottlenose dolphins resident in Sarasota Bay, Florida [52,53]. However, the scientific community should first explore whether and how the values of any parameter estimated in a specific context can be robustly extrapolated to other unsampled or less known species, where tolerance towards disturbance could also vary.…”

Exposure to Novel Parainfluenza Virus and Clinical Relevance in 2 Bottlenose Dolphin (Tursiops truncatus) Populations

“…Blood samples from free-ranging dolphins were obtained as part of a long-term health assessment conducted near Sarasota, involving a multigenerational resident population of ≈150 dolphins (8). Most of these dolphins are recognizable; are of known age, gender, and maternal lineage; and medical histories have been recorded for many years.…”

“…TtPIV-1 may provide similar protection in humans. Dolphins have been recognized as useful marine ecosystem sentinels (8), and changes in marine PIV may refl ect changes in terrestrial PIV.…”