Delta Primary Production
Primary Production, the amount of tissue generated by photosynthetic organisms (e.g., plants and algae) over time, forms the basis of food webs. The Sacramento-San Joaquin Delta has unusually low primary productivity relative to other estuaries (Cloern et al. 2014, Jassby et al. 2002). Food availability has been identified as one contributor to the multi-stressor problem of pelagic organism decline in the Delta (Baxter et al. 2010). But, the constraints on primary production and the relative importance of different production sources to the food web are major uncertainties in this system. Landscape configuration and hydrodynamics are major drivers of primary production dynamics, and understanding how the extensive historical changes in the Delta’s landscape have altered the system’s potential for supporting wildlife and human populations can inform restoration planning and management across the region. Investigating basics about primary production in the Delta can guide us towards better restoration and management decisions.
The Delta Primary Production Project is aimed at investigating three topics:
What is the current amount of primary production available for wildlife in the Delta, and how much was available historically? Datasets of historical and modern land cover now available for the Delta provide a unique opportunity to identify the current and historical amount of primary production, which can tell us about future potential. By comparing first-order estimates of primary production among five major groups of primary producers, historically and today, we should be better able to identify the potential food production of different habitat types, and inform restoration actions that could increase food availability for wildlife.
What is the ecological value of the primary production? Production by different types of plants and algae in the Delta can be thought of as a portfolio of food resources, with each type of production providing different nutritional value, in different quantities at different times of year. A resilient portfolio would provide a suite of available food for consumers over time. An approach to estimating the energy available to primary consumers from the five producer groups would be to determine the caloric value for each type of producer in a ‘common currency’ (kcal or grams of Carbon/m-2/yr-1) based on its biochemical properties, then applying a trophic transfer efficiency to these estimates.
How does physical transport of water between habitats affect food production in the Delta? The estimates of primary production and their food value to consumers provide a ‘static’ picture of food web dynamics. Yet, landscape morphology and local transport of water between wetland and aquatic areas affect residence time, area and magnitude of tidal exchanges, and mixing of water, which in turn affect processes of primary production. A first step in investigating the effects of transport on primary production is to develop a simple model that investigates only two factors: the exchange of water between channel and marsh habitats, and their effects on phytoplankton production.
Delta Primary Production Workshop. In October 2015, a group of national experts convened at SFEI to develop a science plan that would provide first-order estimates of Delta primary production, historically and today. The workshop was funded by the Delta Science Program and USGS.
Detailed summaries of the science plan are available in an essay, “Primary Production in the Delta: Then and Now” (Cloern et al. 2016) and a workshop summary “Primary Production in the Sacramento-San Joaquin Delta”. Both are also available in the "Resources" tab.
Delta Primary Production Forum. In January 2017, a group of managers and scientists met in a forum to discuss the science plan generated during the October 2015 workshop. Forum participants were asked to evaluate the merit and potential applications of this approach, and how their input might be solicited as the approach moves forward. Sponsored and hosted by the Delta Science Program, the goal of the Forum was to provide an opportunity to align research questions between scientists and implementers through “co-discovery” (Walker et al. 2002), allowing for implementation partners from agencies and practitioners to be involved in the science process during the early phases of proposed research.
A summary of the forum can be found here.