Ecological and biophysical determinants of primary and secondary production in a coastal marine ecosystem and implications for fish and whales
Dr. Ron Tanasichuk, Fisheries and Oceans Canada, Pacific Biological Station
A major challenge for nearshore oceanography and marine ecology is to learn how the biology of coastal areas is affected by processes on the continental shelf and in the deep sea. The Folger Passage Node supports a multi-disciplinary study of the physical/chemical/biological oceanographic features of the Sound, their role in affecting variability in secondary (euphausiid/zooplankton) productivity, and the consequences for fish, and whale abundance and distribution. In addition, the real-time monitoring of significant events (phytoplankton bloom, storms) provides opportunity to better understand the highly variable coast-shelf transition zone. Finally, the linking of the Folger Passage Node to the other NEPTUNE Nodes will help us learn how continental shelf and deep sea events affect the biological productivity of coasts.
Physical processes governing the circulation of intermediate water and renewal of inlet deep waters will ultimately control many ecosystem parameters by regulating the fluxes of nutrients and particulate (living and non-living). Variability in these processes may then drive variability in phytoplankton and zooplankton timing and abundance. Measurements of currents with ADCPs (Acoustic Doppler Current Profilers) will allow us to quantify the different regimes and their tidal, weekly, seasonal, and interannual variability. The results will tell us more not only about Barkley Sound, but also about all other inlets on the outer coast.
Animals on the seafloor reflect the environment around them. Sessile (non-motile) suspension feeders require a hard surface, and sufficient flow and microplankton in the water column to be able to capture food. Because they cannot move, however, these animals are at the whims of any changes in the water conditions. To some extent they have evolved adaptations that allow them to respond to short term changes in conditions; however, unexpected changes in their environment, over the short or even long term may provoke unusual responses, and even death. Our experiment involves monitoring sessile suspension feeders with a special camera that can image changes in 3 dimensions over time. Our camera will be made of 8 ‘eyes’ all seeing different angles of the animal, and recording them simultaneously. We will view the animal both in time-lapse (to speed up events) and in real-time, and relate changes in behaviour that we observe to changes in flow and turbidity that are recorded with nearby sensors. The Folger Passage Node integrates with an 18-year on-going programme which monitors euphausiid (krill) and zooplankton production along the West Coast of Vancouver Island based on sampling in Barkley Sound. Euphausiid/zooplankton production has varied by 100-fold. Results of the programme have been used to explain variations in herring, and sockeye, chum and coho salmon productivity. The integration of the studies will allow investigators to learn how the ocean affects the production of the key prey for many species of fish, birds and, directly or indirectly, whales.
Underwater acoustic monitoring using NEPTUNE’s Folger Passage Node will provide valuable year-round data on the occurrence of cetaceans in Barkley Sound. A sensitive broadband hydrophone that is optimal for receiving the wide range of vocalizations used by cetaceans will be established at the Node. The hydrophone uses new digital technology that enables a high-speed ethernet-based connection to the NEPTUNE network. It covers a frequency range of 10 Hz to 65 kHz, ensuring that a wide range of cetacean vocalizations will be received, from the extremely low frequency calls of fin whales to the echolocation clicks of dolphins. We will address a variety of questions about the occurrence of cetaceans in the Folger Passage area through acoustic signals received at the node. For example, the winter distribution of salmon-eating resident killer whales on the BC coast is poorly known, but Barkley Sound is a likely hot spot for both the northern and southern resident populations. Resident killer whale pods can be identified from group-specific vocal dialects, and such acoustic identifications will yield new insights into the patterns of use of this area. Mammal-hunting transient killer whales are also found in the Folger Passage area, and their distinctive calls will be used as an indicator of their seasonal occurrence. Other cetaceans that will likely be monitored on the hydrophone system include humpback whales, fin whales, and Pacific white-sided dolphins.
The Folger Passage Node is located at the seaward end of Barkley Sound, British Columbia. Barkley Sound is a large embayment (550 sq. km) on the west coast of Vancouver Island. The physical and chemical characteristics of the Sound are affected by interactions with continental shelf and deep sea waters, as well as wind and freshwater runoff. The Node is in the vicinity of Folger Island.
The instrumentation is as follows:
Investigating the interdisciplinary links between physical and biological processes is inherently cooperative. Making information publicly available will mean exploratory investigations can occur easily, and we hope that this will increase the likelihood of promising collaborations.
Images will be collected by the underwater computer, and picked up immediately by the U of Alberta team who will process the 3D image and return it immediately for storage on the Neptune DMAS. The 3D images can be collected and analysed by others accessing the Neptune server, and observations shared on listserve for the 3D camera. This listserve will generate new ideas on postprocessing of images and the imaging system will evolve to suit different needs, including generation and development of similar systems at other nodes and elsewhere.
The long-term time series of euphausiid/zooplankton size and abundance will be freely available. A key collaboration will be with other scientists to learn if variations in productivity are local, relatively wide-ranging, or even global. Detailed sampling information will allow scientists to compare information on the population biology of some euphausiid species and a wide variety of zooplankton species.
The underwater acoustic signal from the Folger Passage Node will be streamed live to the Bamfield Marine Sciences Centre and hopefully the internet so that students and marine mammal researchers will be able to listen for their species of interest. The archived broadband acoustic signal will also be freely available for more advanced analyses.