Spatial variability of the photosynthetic parameters and biomass of the Gulf of California phytoplankton

Spatial variability of the central Gulf of California (CGC) phytoplankton biomass and photosynthetic parameters in relation to physical forcing was studied. Sampling was carried out in November, and the surface TC range was 20-27.5°C. Strong tidal mixing in the midrift islands regions injects relatively cool, nutrient-rich waters to the euphotic zone. Some of this water is transported via jets and cool filaments throughout the Gulf. In general, chlorophyll a (Chl) of small phytoplankton (<8 m) (up to >2.5 mg m^-3) was higher than that of large phytoplankton. Highest values of phytoplankton assimilation numbers (P^Bm) [3.17 mg C (mg Chla)^-1 h^-1], and photosynthetic efficiency ^B) [0.23 mg C (mg Chl a)^-1 h^-1 (W m^-2)^-1] were determined for the large phytoplankton cells (>8 m). Our hypothesis that P^Bm values increase from cooler to warmer waters is not supported by the data. We found a 27-fold spatial difference of Chl, compared with a 10-fold difference of P^Bm and a 6-fold difference of ^B. Thus, in our study area, the major source of variability for primary productivity (PP) comes from Chl, and not from P^Bm and ^B. Therefore, we propose that it is possible to estimate late-fall PP for the CGC using average photosynthetic parameters. Average values for P^Bm and ^B of total phytoplankton were 0.72 mg c (mg Chl a)^-1 h^-1 and 0.12 mg C (mg Chl a^-1 h^-1, (W m^-2)^-1, with standard errors of 0.07 and 0.03, respectively.      

Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current

Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity.