Phytoplankton community ecology: principles applied in San Francisco Bay

Abstract

In his seminal 1961 paper 'The paradox of the plankton' Am Nat 95:137-147, G. E. Hutchinson asked why many species of phytoplankton can coexist while competing for a small number of limiting resources in an unstructured habitat. Hutchinson anticipated the resolution of his paradox, recognizing that communities are organized by processes beyond resource competition including species interactions, habitat variability and dispersal. Since 1961 we have made fundamental discoveries that have revolutionized our conceptual understanding of pelagic ecology, including (1) habitat heterogeneity at all scales relevant to plankton population dynamics, (2) community shifts in response to global climate cycles, (3) fast and selective predation as a powerful top-down force to shape phytoplankton communities, (4) turbulent mixing as a physical process that selects species on the basis of their size and form, (5) mixotrophy that allows some algal species to tap organic nutrient pools and function at multiple trophic levels, (6) taxon-specific life cycles including alternating vegetative and resting stages, and (7) the pelagic as an open system where communities are continually reshaped by species immigration. Here we synthesize these discoveries to show how they validate and amplify Hutchinson's hypothesis that phytoplankton communities are assembled by many processes. Our synthesis is built around observations of phytoplankton species composition from a decade of study in San Francisco Bay, used as a case study to illustrate the contemporary principles of phytoplankton community ecology. We apply these principles to address 2 central questions:

Modeled phytoplankton diversity and productivity in the California Current System

“…The transition at which 50% of modeled biomass comprises small cells was approximately 1 mg Chl m −3 , which lies in between the higher value for the CCS (Chavez et al, 1991;Bruland et al, 2001) and 0.3 mg Chl m −3 reported generally for open ocean and coastal waters by Agawin et al (2000). The ability of the model to depict this structure in the phytoplankton community supports the first two principles of phytoplankton community assembly proposed by Cloern and Dufford (2005) (i.e., (1) cell size is determined by nutrient supply and selective grazing and (2) diatoms respond rapidly to nutrient pulses), and lays the foundation for an accurate representation of phytoplankton diversity in the CCS.…”

“…Nonetheless, this modeled diversity is still considerably less than the number of organisms documented in CCS field studies (Balech, 1960;Bolin and Abbott, 1963;Venrick, 2009) and analysis of the San Francisco bay, a CCS-influenced inlet (Cloern and Dufford, 2005). We believe this difference results from two factors.…”

“…In limited geographic regions, these numbers are reduced but still high. Cloern and Dufford (2005) observed approximately 500 distinct phytoplankton taxa within the San Francisco Bay estuary and Venrick (2009) documented nearly 300 phytoplankton taxa in the California Current eastern boundary upwelling system.…”

Metabolic fingerprinting reveals differences between northern and southern strains of the cryptic diatomChaetoceros socialis

“…It is commonly found in the Arctic (Degerlund & Eilertsen, 2010) and also encountered in the Antarctic (Olguin & Alder, 2011), but also reported from San Francisco Bay (Cloern & Dufford, 2005), Mangalore in India (Ha¨rnstro¨m et al, 2007) and the Gulf of Naples (Ribera D' Alcala et al, 2004). Lauder originally described the species in 1864 on material sampled from the South China Sea close to Hong Kong.…”

Lagoon of Venice ecosystem: Seasonal dynamics and environmental guidance with uncertainty analyses and error subspace data assimilation

“…For example, even in regions where important monitoring programs have been operating, and relatively ''rich'' data sets exist, typically, monthly snapshots of the coastal system are collected, but each snapshot is made of a small number of observation points [e.g., Cloern and Dufford, 2005;Testa et al, 2008]. Traditional ways to extend the observations, punctual in time and space, to the whole monitoring region is through geostatistic methods, such as gridding, krigging or objective analysis [Bretherton et al, 1976;Chiles and Delfiner, 1999].…”