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Smith, RC, Baker KS, Dierssen HM, Stammerjohn SE, Vernet M.  2001.  Variability of primary production in an Antarctic marine ecosystem as estimated using a multi-scale sampling strategy. American Zoologist. 41:40-56.   10.1668/0003-1569(2001)041[0040:voppia]2.0.co;2   AbstractWebsite

A major objective of the multidisciplinary Palmer Long Term Ecological Research (LTER) program is to obtain a comprehensive understanding of various components of the Antarctic marine ecosystem-the assemblage of plants, animals, ocean, sea ice, and island components south of the Antarctic Convergence. Phytoplankton production plays a key role in this polar ecosystem, and factors that regulate production include those that control cell growth (light, temperature, nutrients) and those that control cell accumulation rate and hence population growth (water column stability, advection, grazing, and sinking). Several of these factors are mediated by the annual advance and retreat of sea ice. In this study, we examine the results from nearly a decade (1991-2000) of ecological research in the western Antarctic Peninsula region. We evaluate the spatial and temporal variability of phytoplankton biomass (estimated as chlorophyll-a concentration) and primary production (determined in-situ aboard ship as well as estimated from ocean color satellite data). We also present the spatial and temporal variability of sea ice extent (estimated from passive microwave satellite data). While the data record is relatively short from a long-term perspective, evidence is accumulating that statistically links the variability in sea ice to the variability in primary production. Even though this marine ecosystem displays extreme interannual variability in both phytoplankton biomass and primary production, persistent spatial patterns have been observed over the many years of study (e.g., an on to offshore gradient in biomass and a growing season characterized by episodic phytoplankton blooms). This high interannual variability at the base of the food chain influences organisms at all trophic levels.

Montes-Hugo, MA, Vernet M, Martinson D, Smith R, Iannuzzi R.  2008.  Variability on phytoplankton size structure in the western Antarctic Peninsula (1997-2006). Deep-Sea Research Part Ii-Topical Studies in Oceanography. 55:2106-2117.   10.1016/j.dsr2.2008.04.036   AbstractWebsite

The temporal and spatial variability of phytoplankton size structure of waters west of the Antarctica Peninsula (WAP) was investigated between 1997 and 2006. Time series of satellite-derived (phytoplankton size structure index or gamma b(bp), chlorophyll a concentration or chl(T), and sea-ice extent) and shipboard (temperature, salinity, nutrients, and mixed-layer depth) variables were generated during spring-summer in slope, middle shelf and inshore waters and analyzed in relation to atmospheric anomalies (El Nino Southern Oscillation, ENSO, and Southern Annular Mode, SAM). The sampling design included stations north (northern, 62 degrees S) and within (central and southern, 64-68 degrees S) the Pal-LTER (Palmer Long Term Ecological Research) study site. It is hypothesized that contribution of 'small' phytoplankton (< 20 mu m) has increased in the last decade in WAP waters due the ongoing regional climate change. Relationships between gamma b(bp) the spectral slope of particle backscattering, and environmental parameters were explored based on non-parametric trends (Mann-Kendall test) and cross-correlation coefficients (Spearman matrix). Three types of temporal patterns were detected in satellite-derived phytoplankton size distributions: (1) inter-annual variations of spring-summer gamma b(bp) related to monthly sea-ice extent, (2) abrupt transitions toward dominance of 'small' (<20gm) phytoplankton cells (high gamma b(bp)) and low chI(T) values ( < 1 mg m(-3)) during 1998 and 2003 summer seasons, and (3) positive or negative trends (decrease vs increase of mean cell size) in specific domains of central and northern stations. Temporal transitions in cell size coincided with a switch on ENSO and SAM anomalies as well as increase of heat content of shelf waters over the WAP region. The lack of offshore spring bloom and summer shelf bloom most likely explains the dominance of relative small phytoplankton cells during the 1998 and 2003 summer seasons. A greater frequency of southerly winds during spring and autumn is expected to favor the dominance of 'small' (< 20 mu m) phytoplankton cells over WAP waters. Conversely, the greater intensification of the Antarctic Circumpolar Current interaction with the WAP shelf-break during SAM+ years is expected to intensify topographically induced upwelling and favor the dominance of 'large' ( > 20 mu m) phytoplankton cells on slope waters of central stations. The well-described 50-year warming trend in the Antarctic Peninsula has not resulted in a consistent trend in phytoplankton size structure, as originally hypothesized, but a mosaic of trends attributed to anomalous mesoscale changes of sea-ice extent and circulation patterns. (C) 2008 Published by Elsevier Ltd.

Ferrero, E, Eory M, Ferreyra G, Schloss I, Zagarese H, Vernet M, Momo F.  2006.  Vertical mixing and ecological effects of ultraviolet radiation in planktonic communities. Photochemistry and Photobiology. 82:898-902.   10.1562/2005-11-23-ra-736   AbstractWebsite

We present a mathematical model for a phytoplankton-zooplankton system, based on a predator-prey scheme. The model considers the effects of sinking in the phytoplankton, vertical mixing and attenuation of photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) in the water column. In a first approach, the model was studied under conditions of average PAR irradiance and shows fluctuations and stable equilibrium points. Secondly, we introduced the effects of photoperiod and photoinhibition by UVR and vertical mixing. Under these conditions, the phytoplankton biomass oscillates depending on the combined effects of UVR and mixing. Higher inhibition by UVR and longer mixing periods can induce strong fluctuations in the system but can also produce higher plankton peaks.