Abstract Title

Session S-01D: Pelagic Ecology in the Salish Sea I

Presenter/Author Information

Gus RobertsonFollow

Keywords

Species and Food Webs

Start Date

1-5-2014 5:00 PM

End Date

1-5-2014 6:30 PM

Description

The Puget Sound is experiencing Harmful Algal Bloom (HAB) events of increasing frequency, distribution and severity. To determine the causes for these increases and if human activities are involved, it is important to determine the natural seasonal variations of phytoplankton species composition, abundance and biomass. A challenge of making these measurements is the dynamic nature of the Puget Sound estuaries. Circulation and vertical mixing by riverflow, waves, wind and tides can result in substantial spatial heterogeneity (patchiness) in the distribution of phytoplankton. This patchiness has important consequences for the selection of sampling sites and how the data from these sites is used to infer changes over larger space scales. This study examined the changes in phytoplankton biomass (estimated from chlorophyll a measurements), species composition, and abundance of the dominant species at two locations in Budd Inlet (South Puget Sound) during summer of 2013. Plankton samples were collected weekly. In addition, three separate studies were conducted to examine the variations in phytoplankton parameters over (1) short space scales (tens of meters), (2) within a 12-hour tidal cycle (high, low, incoming, outgoing stages), and (3) at various depth of the water column. Notable findings from this study were the presence of Akashiwo sanguinea throughout summer. Typically Ceratium fusus is the dinoflagellate that dominates during this time of the year and the presence of A. sanguinea may indicate a shift in the species composition. In mid summer, there was an unexpected increase in diatoms, but there was no obvious environmental change preceding this event. The patchiness studies revealed significant variations over short time and space scales. Some of the patterns observed could be explained by the circulation patterns of the sampling sites and dinoflagellate vertical migrations. The magnitude of patchiness observed in this study underscores the importance of considering the physical dynamics of the environment when interpreting data collected from single stations.

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May 1st, 5:00 PM May 1st, 6:30 PM

Phytoplankton temporal and spatial variations in Budd Inlet, south Puget Sound during summer 2013

Room 6C

The Puget Sound is experiencing Harmful Algal Bloom (HAB) events of increasing frequency, distribution and severity. To determine the causes for these increases and if human activities are involved, it is important to determine the natural seasonal variations of phytoplankton species composition, abundance and biomass. A challenge of making these measurements is the dynamic nature of the Puget Sound estuaries. Circulation and vertical mixing by riverflow, waves, wind and tides can result in substantial spatial heterogeneity (patchiness) in the distribution of phytoplankton. This patchiness has important consequences for the selection of sampling sites and how the data from these sites is used to infer changes over larger space scales. This study examined the changes in phytoplankton biomass (estimated from chlorophyll a measurements), species composition, and abundance of the dominant species at two locations in Budd Inlet (South Puget Sound) during summer of 2013. Plankton samples were collected weekly. In addition, three separate studies were conducted to examine the variations in phytoplankton parameters over (1) short space scales (tens of meters), (2) within a 12-hour tidal cycle (high, low, incoming, outgoing stages), and (3) at various depth of the water column. Notable findings from this study were the presence of Akashiwo sanguinea throughout summer. Typically Ceratium fusus is the dinoflagellate that dominates during this time of the year and the presence of A. sanguinea may indicate a shift in the species composition. In mid summer, there was an unexpected increase in diatoms, but there was no obvious environmental change preceding this event. The patchiness studies revealed significant variations over short time and space scales. Some of the patterns observed could be explained by the circulation patterns of the sampling sites and dinoflagellate vertical migrations. The magnitude of patchiness observed in this study underscores the importance of considering the physical dynamics of the environment when interpreting data collected from single stations.