Seals as collectors of oceanographic data in the coastal zone

Abstract

Understanding spatial and temporal variation in water temperatures in the coastal zone is generally limited, as conventional monitoring platforms often prove problematic in these areas, e.g. shallow depths limit access by research vessels, and issues of accuracy and resolution can affect the use of remotely sensed sea-surface temperature data. As a result most currently available data on sea temperature are from offshore waters while coastal areas have remained relatively unexplored. Water temperature is an important parameter to study in these coastal waters, considering its impact and influence on the timing and frequency of harmful algal blooms and their associated impacts on aquaculture. It is a significant factor in the timing of the spring bloom and primary productivity, with consequent influences on the entire marine food web. Advances in bio-logging technologies in recent years have provided opportunities for sensor deployment on a variety of marine animals, including marine mammals, sea birds, fish and turtles, to gather data from inaccessible areas. In this study, we explored the use of telemetry-derived data from instrumented seals in Kenmare Bay in southwest Irish waters to ascertain if seals can be used as sampling platforms in oceanographic studies in the coastal zone and to examine fine scale changes in water temperatures. High spatial and temporal measurements allowed the characterisation of the water dynamics in the estuarine area by the identification of processes such as thermal stratification, up/downwellings and the onset of the thermocline, and provide unique insights into the marine environment in and around the bay, where no previous oceanographic studies have been conducted. Strong correlation between the seal-derived temperature data and in situ temperature recorders and modelled data validates the use of seals as oceanographic platforms on different spatial scales.