Abstracts

03/26/09: Coupled biophysical modeling in the Northern California Current: GLOBEC results and future directions

More than a decade of US GLOBEC funding of model and field investigations has improved knowledge on atmospherically-forced patterns of circulation and hydrography in the Northern California Current, and how physical processes interact with ecology to structure continental shelf pelagic ecosystem dynamics and function. Results of coupled biophysical models are highly dependent on having realistic simulations of the ocean physics. This talk will summarize some of the results of GLOBEC's modeling investigations in the Northeast Pacific. How the physical and ecosystem models may be used to answer climate- and conservation-related societal needs will be addressed. Directions for future coupled biophysical models of the Oregon shelf region, including real-time forecasts of the production and fate of shelf primary production and its effects on dissolved oxygen concentration and incipient hypoxic conditions will be outlined.

03/31/09: Global Climate Variability and its Impacts on North Pacific Ecosystem

One on the important legacies of the US GLOBEC program is that it has advanced our view of climate-ecosystem linkages from a simplistic correlative relationship to one that recognizes and understands the mechanisms by which global climate variability drives changes in regional ecosystem productivity and structure. This talk will describe the multiple approaches to and results of recent work by GLOBEC scientists and colleagues to decipher the patterns in time and space that characterize environmental variability and climate change. Spatial variability from global down to sub-ecosystem scales is important in driving ecosystem processes. Temporal variability includes not only natural interannual to centennial cycles and an apparent anthropogenic global climate change trend, but shifts in seasonal cycles that are critical for the life histories of many managed and protected populations. These analyses have helped us to understand the relationships between past climate and ecosystem variability, and allowed scientists to develop indicators that summarize and assess ecosystem state. Many of these indicators are now being implemented.

04/01/09: Climate change, marine food webs and survival of juvenile salmon during the first summer at sea in the northern California Current

Long-term sampling of hydrography and zooplankton at biweekly intervals in the coastal upwelling zone off Oregon for the past 13 years has shown that variations in copepod biodiversity, species richness and community structure are highly-correlated with the PDO. When the PDO is in negative phase (as in 1999-2002), waters from the Gulf of Alaska feed the northern California Current (NCC) and transport large, lipid-rich copepods to the shelf waters of the NCC; when the PDO is positive (as in 2003-2006), waters from offshore and south feed the NCC and transport small, oceanic lipid-poor copepods to the coast. Thus the forces that drive the PDO, basin scale variations in wind, result in local food chains with vastly different bio-energetic content. These signals may be transmitted up the food chain to salmon since interannual variations in salmon returns are highly-correlated with biomass of "northern" lipid-rich zooplankton species. Thus, knowledge of source waters which feed the NCC is critical for understanding ecosystem dynamics in the shelf waters of the NCC. A comparison of hydrographic and zooplankton data from the 1960s and 1970s with recent data, shows that the Northern California Current ecosystem is becoming more subtropical in nature, likely due to climate change.

04/08/09: Salmon population dynamics in the Pacific Northwest

The relative roles of the physical environment and fishing on fish populations is a question that has attracted scientific attention since the mid nineteenth century. Answering this question requires an understanding of the population dynamics of the species of interest. While we know that the direct effect of fishing is on mortality, the environment can affect growth and mortality rates at specific stages in their life history, and these points of action have different implications for expected population changes. In this talk I will trace our development of an understanding of salmon population dynamics from the beginning of the North East Pacific (NEP) GLOBEC program to the Pan Regional Synthesis beginning this year. In the NEP, coho salmon appeared to respond differently to the regime shift in the mid-1970s, offering the valuable opportunity for comparative research. Coho salmon catches showed a clear inverse relationship between Alaska and the California Current, while chinook salmon catches did not. The major population dynamic difference between species, a difference in spawning age distribution, was shown not to provide a clear explanation for this difference. More recent analysis of coho salmon survivals from coded wire tag data (1982-2004) showed a lack of inverse covariability between Alaska and the California Current, rather spatial covariability among survivals over 100 km scales, i.e., local regional scales rather than semi-basin scales. We are currently engaged in modeling studies showing how: (1) the life history point of action of environmental forcing (i.e., mortality or growth rate at age), (2) the variable observed (i.e., recruitment, abundance, catch), and (3) changes long-term survival (as caused by fishing or slow climate change) caused different population responses in Pacific salmon. The direct practical application of our work has been in: (1) assistance in debunking a publication that attempted to reduce the range of the ESA-listed southern coho salmon, and (2) reminding finger-pointing stakeholders in salmon disputes that it is the sum of all sources of mortality that cause declines, not a single cause (e.g., fishing, diversions, dams, etc.)

04/29/09: Structuring of Southern Ocean food webs: highlights from Southern Ocean GLOBEC

Some of the strongest regional expressions of global climate change have occurred in the Southern Ocean. Changes to the environment, including modifications in sea ice extent and concentration, have been associated with variations in ecosystems and biogeochemical processes. The region is characterized by unique food webs, is an important component of the global carbon cycle, and supports commercially harvested species. Understanding climate-induced changes and their consequences for food webs and biogeochemical cycling is integral to predicting the impacts and feedbacks of the Southern Ocean as part of the Earth System, and to developing sustainable management for the region. Fundamental to predicting how ecosystems respond to change is an understanding of food web structure and function. This requires synthesis of current knowledge of Southern Ocean food webs and modeling approaches. This presentation will review the status of Southern Ocean food web models and explore issues associated with developing these to the circumpolar scale. The gaps in knowledge that limit current food web models will be highlighted with particular emphasis on the importance of considering regional and trophic complexities. Multidisciplinary modeling approaches that bring together different scales and processes will be discussed with a particular focus on the development of end-to-end food web models for the Southern Ocean.