Before graduate studies Joel spent 8 years working in First Nation’s communities on BC’s central coast. His work was primarily in fisheries stock assessment, industrial impact assessments and rehabilitation research for species at risk. He began his PhD with John Reynolds in 2008 to pursue his interest in landscape connectivity, nutrient dynamics and the role of pacific salmon in coastal ecosystems.
The flow and availability of resources, or the ‘connectivity’ in ecological systems has been a major theme in ecology. A large body of research has demonstrated that resource availability is a fundamental force shaping ecological systems, and that this availability can be largely dependent on subsidies from adjacent habitats. How food webs respond to resource subsidies can also depend greatly on the spatial and temporal scales at which a subsidy exists, and whether such scales are significant to the individuals and communities of recipient habitats. The central coast of BC is an extremely dynamic and awe-inspiring natural landscape. The movement of material from upstream headwaters to the coast and the ‘counter-flow’ annual pulses of returning salmon, provide an amazing opportunity to study the movement of material between landscapes.
My thesis is exploring the influence of nutrient export from coastal watersheds to estuaries and the relative importance of salmon as a nutrient subsidy amongst these background dynamics. I study across a broad gradient of watershed sizes that host different hydrological regimes, riparian communities and salmon densities to gain a better understanding of how upstream landscapes influence what position an estuary occupies along the terrestrial-marine continuum, and the importance of salmon subsides in these transitional ecosystems that extend well beyond streams and riparian zones. The goal of this work is to demonstrate the importance of cross-ecosystem nutrient linkages and the intimate relationships between estuaries, upstream landscapes and oceans by way of annual salmon runs.
Kayi Chan is a Masters student in the Department of Biological Sciences at Simon Fraser University. Her research focuses on invasive bivalves and their effects on biogeochemical cycling of nutrients in the intertidal. Kayi finished her honours project at Simon Fraser University in 2005 which examined the role of the invasive Manila clam on ammonium flux. Her current project is examining how the varnish clam has altered nutrient cycling in the intertidal and the ecosystem consequences.
Since the advent of nautical travel, humans have been transporting organisms into novel environments with little understand of the consequences. The introduction of an invasive bivalve can have devastating consequences for an ecosystem. The invasion of San Francisco Bay by the Asian clam, Corbula amurensis, led to the collapse of the fisheries industry and a dramatic change in the ecosystem functioning of the intertidal system there. My thesis focuses on the consequences of the establishment of the invasive bivalve, Nuttallia obscurata, on sediment characteristics in the intertidal area. The varnish clam, N. obscurata, was first reported in the early 1990s and is believed to have been introduced via ballast waters into Vancouver Harbour, British Columbia (BC) from its native habitat in the Northwest Pacific. It has since spread rapidly reaching up to Smith Sound, BC in the north and down to Coos Bay, Oregon in the south at densities reported as high as 800 individuals/m2. I applied a 3-tiered approach, which consisted of a field survey (Tier I), a density manipulation experiment (Tier II) and a microcosm experiment (Tier III). From my field survey, I found a trend of increasing organic matter content with increasing bivalve densities at mid sediment depths (3-6 cm). An increase in organic matter content could lead to over-enrichment of sediments, which could lead to anoxia that would result in the change of the redox potentials of the sediments. I found a trend of higher organic matter with high varnish clam densities (Tier II). I also found significantly higher ammonium levels with high densities (Tier II) and showed that the increase in ammonium was due to the excretory processes of the varnish clam (Tier III). Nitrogen is a limiting nutrient in marine systems, with ammonium being the form of nitrogen that is preferentially uptaken by phytoplankton. A change in the flux of nitrogen as well as an accumulation of organic matter would result in drastic changes to ecosystem functioning in the intertidal. Given that varnish clams are often found with the economically important Manila clams, Tapes philippinarum, the results of my research could have consequences for the aquaculture industry on the BC coast.
Brendan Connors is a Postdoctoral fellow in the School of Resource & Environmental Management at Simon Fraser University. Brendan's research focuses on understanding how natural and human mediated processes interact to shape ecological dynamics. Brendan completed his PhD in Ecology at Simon Fraser University in 2010 which focused on understanding the role parasite behaviour plays in mediating the establishment of infectious disease and how this in turn structures parasite and host populations, communities and dynamics. His current research includes studying disease-mediated interactions between wild and farmed salmon and epidemiological approaches to ecosystem health.
Parasitism is the most common animal lifestyle yet surprisingly little is known about the role parasites play in the ecosystems in which they are embedded. This thesis examines the causes and consequences of the dispersal of a marine ectoparasite, the salmon louse (Lepeophtheirus salmonis), in an area of intensive salmon aquaculture where the transmission of lice from farmed salmon may have consequences for the dynamics of adjacent wild salmon populations. Salmon lice are capable of leaving one host in search of another as they approach sexual maturity; while previously thought to be an artefact of the confined conditions characteristic of experiments and salmon farms I show that this is common in nature with at least 50% of lice on juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon moving from one host to another as they mature. I demonstrate that the underlying drivers of this dispersal shift with ontogeny from competition for resources to access to mates. Movement among hosts increases the probability that a louse interacts with multiple hosts potentially increasing the extent of louse transmission from farmed to wild salmon and the spread of other pathogens if lice can act as vectors. In addition, the movement of lice among hosts may have important consequences for predator-prey interactions between salmonids during early marine life. Coho salmon smolts (O. kisutch) selectively prey upon infected pinks. I show that sea lice transfer from pinks to coho during these interactions and as a result coho experience a 2 to 3 fold increase in parasite exposure over what they would otherwise experience through passive exposure to infective larvae from farms. To test for a population level response to this increase in louse exposure I examined coho population dynamics spanning a region of exposure to lice from infected pink salmon and salmon farms and show that populations exposed to recurrent infestations were depressed 7 fold relative to adjacent unexposed populations. These findings highlight the ecosystem context in which louse transmission from farmed to wild fish occurs and suggest that species interactions and parasite behaviour may cause the effects of parasite transmission from farmed to wild fish to propagate up marine food webs with broader consequences than previously appreciated.