Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current

Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255–257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We show how a 1-month delay in the 2005 spring transition to upwelling-favorable wind stress in the northern California Current Large Marine Ecosystem resulted in numerous anomalies: warm water, low nutrient levels, low primary productivity, and an unprecedented low recruitment of rocky intertidal organisms. The delay was associated with 20- to 40-day wind oscillations accompanying a southward shift of the jet stream. Early in the upwelling season (May–July) off Oregon, the cumulative upwelling-favorable wind stress was the lowest in 20 years, nearshore surface waters averaged 2°C warmer than normal, surf-zone chlorophyll-a and nutrients were 50% and 30% less than normal, respectively, and densities of recruits of mussels and barnacles were reduced by 83% and 66%, respectively. Delayed early-season upwelling and stronger late-season upwelling are consistent with predictions of the influence of global warming on coastal upwelling regions

Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current

Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255–257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We show how a 1-month delay in the 2005 spring transition to upwelling-favorable wind stress in the northern California Current Large Marine Ecosystem resulted in numerous anomalies: warm water, low nutrient levels, low primary productivity, and an unprecedented low recruitment of rocky intertidal organisms. The delay was associated with 20- to 40-day wind oscillations accompanying a southward shift of the jet stream. Early in the upwelling season (May–July) off Oregon, the cumulative upwelling-favorable wind stress was the lowest in 20 years, nearshore surface waters averaged 2°C warmer than normal, surf-zone chlorophyll-a and nutrients were 50% and 30% less than normal, respectively, and densities of recruits of mussels and barnacles were reduced by 83% and 66%, respectively. Delayed early-season upwelling and stronger late-season upwelling are consistent with predictions of the influence of global warming on coastal upwelling regions.Keywords: coastal ocean upwelling, coastal marine ecosystems, marine ecology, climate variabilit

Larval dispersal in a changing ocean with an emphasis on upwelling regions

Dispersal of benthic species in the sea is mediated primarily through small, vulnerable larvae that must survive minutes to months as members of the plankton community while being transported by strong, dynamic currents. As climate change alters ocean conditions, the dispersal of these larvae will be affected, with pervasive ecological and evolutionary consequences. We review the impacts of oceanic changes on larval transport, physiology, and behavior. We then discuss the implications for population connectivity and recruitment and evaluate life history strategies that will affect susceptibility to the effects of climate change on their dispersal patterns, with implications for understanding selective regimes in a future ocean. We find that physical oceanographic changes will impact dispersal by transporting larvae in different directions or inhibiting their movements while changing environmental factors, such as temperature, pH, salinity, oxygen, ultraviolet radiation, and turbidity, will affect the survival of larvae and alter their behavior. Reduced dispersal distance may make local adaptation more likely in well-connected populations with high genetic variation while reduced dispersal success will lower recruitment with implications for fishery stocks. Increased dispersal may spur adaptation by increasing genetic diversity among previously disconnected populations as well as increasing the likelihood of range expansions. We hypothesize that species with planktotrophic (feeding), calcifying, or weakly swimming larvae with specialized adult habitats will be most affected by climate change. We also propose that the adaptive value of retentive larval behaviors may decrease where transport trajectories follow changing climate envelopes and increase where transport trajectories drive larvae toward increasingly unsuitable conditions. Our holistic framework, combined with knowledge of regional ocean conditions and larval traits, can be used to produce powerful predictions of expected impacts on larval dispersal as well as the consequences for connectivity, range expansion, or recruitment. Based on our findings, we recommend that future studies take a holistic view of dispersal incorporating biological and oceanographic impacts of climate change rather than solely focusing on oceanography or physiology. Genetic and paleontological techniques can be used to examine evolutionary impacts of altered dispersal in a future ocean, while museum collections and expedition records can inform modern-day range shifts

Regional and seasonal patterns of epipelagic fish assemblages from the central California Current

The coastal Pacific Ocean off northern and central California encompasses the strongest seasonal upwelling zone in the California Current ecosystem. Headlands and bays here generate complex circulation features and confer unusual oceanographic complexity. We sampled the coastal epipelagic fish community of this region with a surface trawl in the summer and fall of 2000–05 to assess patterns of spatial and temporal community structure. Fifty-three species of fish were captured in 218 hauls at 34 fixed stations, with clupeiform species dominating. To examine spatial patterns, samples were grouped by location relative to a prominent headland at Point Reyes and the resulting two regions, north coast and Gulf of the Farallones, were plotted by using nonmetric multidimensional scaling. Seasonal and interannual patterns were also examined, and representative species were identified for each distinct community. Seven oceanographic variables measured concurrently with trawling were plotted by principal components analysis and tested for correlation with biotic patterns. We found significant differences in community structure by region, year, and season, but no interaction among main effects. Significant differences in oceanographic conditions mirrored the biotic patterns, and a match between biotic and hydrographic structure was detected. Dissimilarity between assemblages was mostly the result of differences in abundance and frequency of occurrence of about twelve common species. Community patterns were best described by a subset of hydrographic variables, including water depth, distance from shore, and any one of several correlated variables associated with upwelling intensity. Rather than discrete communities with clear borders and distinct member species, we found gradients in community structure and identified stations with similar fish communities by region and by proximity to features such as the San Francisco Bay

Physical Factors Influencing Phytoplankton Abundance in Southern Monterey Bay

As the base of almost all marine food webs, phytoplankton play a dominant role in determining the productivity of marine ecosystems. Recent studies have highlighted the dynamic variability of phytoplankton abundance in nearshore ecosystems over synoptic time scales. The inability of satellite ocean color monitoring to resolve chlorophyll values at a resolution less than 1 km and a reliable temporal resolution of ~8 days means this data cannot adequately capture the impact of nearshore dynamics on chlorophyll abundance and distribution. Therefore, a greater understanding of the physical mechanisms that contribute to this variability is required to assess impacts of current as well as future weather patterns on these ecosystems. In this study, chlorophyll fluorescence data from a nearshore location in the south Monterey Bay was used to identify the timing and duration of increases in phytoplankton concentrations. Physical parameters, including wind stress and water temperature were analyzed to determine whether upwelling and/or upwelling relaxation events correlate with observed blooms. A significant negative correlation between water temperature and chlorophyll was found for the two summer seasons studied (2012, 2013) which suggess that increases in chlorophyll concentrations are more likely due to advection than biological reproduction. The results of this study suggest that phytoplankton are advected into the southern Monterey Bay during wind relaxation events of great enough magnitude to disrupt dominant circulation patterns. These impacts are site specific and demonstrate the degree to which the ecological subsidies can vary over small spatial ranges at synoptic scales

Ecological linkages: Marine and estuarine ecosystems of Central and Northern California

Three of California’s four National Marine Sanctuaries, Cordell Bank, Gulf of the Farallones, and Monterey Bay, are currently undergoing a comprehensive management plan review. As part of this review, NOAA’s National Marine Sanctuary Program (NMSP) has collaborated with NOAA’s National Centers for Coastal Ocean Science (NCCOS) to conduct a biogeographic assessment of selected marine resources using geographic information system (GIS) technology. This report complements the analyses conducted for this effort by providing an overview of the physical and biological characteristics of the region. Key ecosystems and species occurring in estuarine and marine waters are highlighted and linkages between them discussed. In addition, this report describes biogeographic processes operating to affect species’ distributional patterns. The biogeographic analyses build upon this background to further understanding of the biogeography of this region. (PDF contaons 172 pages

Examining sources of primary production and bottom-up limitations in nearshore ecosystems of the northeast Pacific Ocean using fish based indicators

Thesis (Ph.D.) University of Alaska Fairbanks, 2015Our ability to forecast the fate of ecosystems and species hinges on an understanding of how biological systems respond to their environment. In this dissertation, natural indicators of diet (stable isotopes) and production (otolith growth increment width) in two common fishes were used to investigate energy pathways and biophysical relationships in nearshore kelp forests spanning two large marine ecosystems with contrasting oceanography, the upwelling system of the California Current and the downwelling system of the Alaska Coastal Current. Stable isotope analysis indicated high proportions of kelp-derived carbon in two common predatory fish, pelagic-feeding Black Rockfish and benthic-feeding Kelp Greenling. Routinely using both kelp and phytoplankton energy channels reflects strong benthic-pelagic coupling in nearshore marine food webs and may confer food web resilience to perturbations in either energy channel. A network of annual otolith growth chronologies were used to test bottom-up limits of production for nearshore systems and later explore other possible correlates of production. Results of hypothesis tests were consistent with bottom-up forcing of nearshore marine ecosystems, with light and nutrients constraining primary production in pelagic food webs and temperature constraining benthic food webs. A separate exploratory analysis indicated that biophysical relationships were common with (1-2 years) and without time lags and suggested that differences in the abundance and quality of prey influenced the growth of fish through bottom-up processes. The findings from the separate exploratory analysis were generally consistent with findings from hypothesis testing. Lagged relationships were consistent with increasing higher nearshore prey abundance during warm conditions in the Alaska Coastal Current and during cool conditions in the California Current in both pelagic and benthic food webs. Relationships without time lags indicated that benthic prey quality increased during warm conditions in both current systems, while the quality of pelagic nearshore prey increased during cool conditions in the California Current and warm conditions in the Alaska Current. Overall, results of this dissertation demonstrate that kelp provides a source of energy to higher trophic level predators and that continued warming will likely have a negative influence at lower latitudes first (e.g., California Current), while production in higher latitudes (e.g., Gulf of Alaska) may initially increase.Chapter 1: Widespread kelp-derived carbon in pelagic and benthic nearshore fishes -- Chapter 2: Evidence of bottom-up limitations in nearshore marine systems based on otolith proxies of fish growth -- Chapter 3: Influence of basin and local-scale conditions on nearshore production in the northeast Pacific Ocean -- Conclusions