Areas of high water residence time are critical to pelagic secondary production in the Fraser River Estuary
Presentation Abstract
Identifying what factors limit a system’s capacity to support higher trophic levels is key to successful environmental restoration. However, studies of pelagic lower trophic levels in the estuaries of British Columbia are limited. Despite supporting economically and culturally important fisheries, the zooplankton dynamics of the Fraser River Estuary have never been described. To catalogue the zooplankton species present in the Estuary and to better understand their dynamics in relation to environmental forcing, we carried out a 30-month monitoring program. Our estimates of zooplankton abundance, biomass, and production are very low in comparison to estuaries worldwide. These low estimates are likely due to the minimal contribution of estuarine endemic zooplankton (a group that typically overwhelmingly dominates the zooplankton community of most estuaries) to total zooplankton abundance. We suggest that channelization and floodplain habitat loss have dramatically lowered pelagic secondary production in this estuary by reducing water residence time. Estuarine endemic zooplankton employ several different strategies to achieve retention within the estuary, as they cannot survive in fully marine waters. Our results suggest that these strategies are unable to overcome losses due to flushing in most areas of the Fraser River Estuary. This is further supported by the higher abundances of estuarine endemics that occur in slough environments, which have higher water residence times. These sloughs are largely man-made, yet they provide a critical refuge allowing the growth of estuarine zooplankton populations. Our results support the importance of the floodplain to estuarine pelagic production but also highlight the need to consider water residence time and the impact on lower trophic levels before opening connections within an estuary.
Session Title
Toward a vision for Ecological Resilience in the Lower Fraser River
Conference Track
Shorelines, Estuaries & Rivers
Conference Name
Salish Sea Ecosystem Conference (2020 : Online)
Document Type
Event
SSEC Identifier
2020_abstractID_4567
Start Date
21-4-2020 9:00 AM
End Date
22-4-2020 4:45 PM
Genre/Form
conference proceedings; presentations (communicative events)
Subjects – Topical (LCSH)
Estuarine restoration-- British Columbia--Fraser River Estuary; Estuarine area conservation--British Columbia--Fraser River Estuary
Geographic Coverage
Salish Sea (B.C. and Wash.); Fraser River Estuary (B.C.)
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Format
application/pdf
Areas of high water residence time are critical to pelagic secondary production in the Fraser River Estuary
Identifying what factors limit a system’s capacity to support higher trophic levels is key to successful environmental restoration. However, studies of pelagic lower trophic levels in the estuaries of British Columbia are limited. Despite supporting economically and culturally important fisheries, the zooplankton dynamics of the Fraser River Estuary have never been described. To catalogue the zooplankton species present in the Estuary and to better understand their dynamics in relation to environmental forcing, we carried out a 30-month monitoring program. Our estimates of zooplankton abundance, biomass, and production are very low in comparison to estuaries worldwide. These low estimates are likely due to the minimal contribution of estuarine endemic zooplankton (a group that typically overwhelmingly dominates the zooplankton community of most estuaries) to total zooplankton abundance. We suggest that channelization and floodplain habitat loss have dramatically lowered pelagic secondary production in this estuary by reducing water residence time. Estuarine endemic zooplankton employ several different strategies to achieve retention within the estuary, as they cannot survive in fully marine waters. Our results suggest that these strategies are unable to overcome losses due to flushing in most areas of the Fraser River Estuary. This is further supported by the higher abundances of estuarine endemics that occur in slough environments, which have higher water residence times. These sloughs are largely man-made, yet they provide a critical refuge allowing the growth of estuarine zooplankton populations. Our results support the importance of the floodplain to estuarine pelagic production but also highlight the need to consider water residence time and the impact on lower trophic levels before opening connections within an estuary.
