scholarly journals Modeling changes in baleen whale seasonal abundance, timing of migration, and environmental variables to explain the sudden rise in entanglements in California

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0248557
Author(s):  
Kaytlin Ingman ◽  
Ellen Hines ◽  
Piero L. F. Mazzini ◽  
R. Cotton Rockwood ◽  
Nadav Nur ◽  
...  
Keyword(s):  
Negative Binomial ◽  
Southern Oscillation ◽  
Current System ◽  
Seasonal Abundance ◽  
Environmental Drivers ◽  
California Current System ◽  
Central California ◽  
Early Arrival ◽  
Basin Scale ◽  
Timing Of Migration

We document changes in the number of sightings and timing of humpback (Megaptera novaeangliae), blue (Balaenoptera musculus), and gray (Eschrichtius robustus) whale migratory phases in the vicinity of the Farallon Islands, California. We hypothesized that changes in the timing of migration off central California were driven by local oceanography, regional upwelling, and basin-scale climate conditions. Using 24 years of daily whale counts collected from Southeast Farallon Island, we developed negative binomial regression models to evaluate trends in local whale sightings over time. We then used linear models to assess trends in the timing of migration, and to identify potential environmental drivers. These drivers included local, regional and basin-scale patterns; the latter included the El Niño Southern Oscillation, the Pacific Decadal Oscillation, and the North Pacific Gyre Oscillation, which influence, wind-driven upwelling, and overall productivity in the California Current System. We then created a forecast model to predict the timing of migration. Humpback whale sightings significantly increased over the study period, but blue and gray whale counts did not, though there was variability across the time series. Date of breeding migration (departure) for all species showed little to no change, whereas date of migration towards feeding areas (arrival) occurred earlier for humpback and blue whales. Timing was significantly influenced by a mix of local oceanography, regional, and basin-scale climate variables. Earlier arrival time without concomitant earlier departure time results in longer periods when blue and humpback whales are at risk of entanglement in the Gulf of the Farallones. We maintain that these changes have increased whale exposure to pot and trap fishery gear off the central California coast during the spring, elevating the risk of entanglements. Humpback entanglement rates were significantly associated with increased counts and early arrival in central California. Actions to decrease the temporal overlap between whales and pot/trap fishing gear, particularly when whales arrive earlier in warm water years, would likely decrease the risk of entanglements.

Nutrient variability during El Niño 1997–98 in the California current system off central California

2002 ◽  
Vol 54 (1-4) ◽  
pp. 171-184 ◽  
Author(s):  
C.G. Castro ◽  
C.A. Collins ◽  
P. Walz ◽  
J.T. Pennington ◽  
R.P. Michisaki ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Current System ◽  
California Current ◽  
California Current System ◽  
Central California ◽  
Nutrient Variability

scholarly journals Resilience and stability of a pelagic marine ecosystem

2016 ◽  
Vol 283 (1822) ◽  
pp. 20151931 ◽  
Author(s):  
Martin Lindegren ◽  
David M. Checkley ◽  
Mark D. Ohman ◽  
J. Anthony Koslow ◽  
Ralf Goericke
Keyword(s):  
Ecosystem Functioning ◽  
Decadal Variability ◽  
Current System ◽  
Marine Ecosystem ◽  
Experimental Studies ◽  
Trophic Levels ◽  
Environmental Drivers ◽  
California Current System ◽  
Functional Complementarity ◽  
Key Species

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS.

Seasonal dynamics of physical and biological processes in the central California Current System: A modeling study

2014 ◽  
Vol 64 (8) ◽  
pp. 1137-1152 ◽  
Author(s):  
Lin Guo ◽  
Fei Chai ◽  
Peng Xiu ◽  
Huijie Xue ◽  
Shivanesh Rao ◽  
...  
Keyword(s):  
Seasonal Dynamics ◽  
Current System ◽  
California Current ◽  
Biological Processes ◽  
California Current System ◽  
Central California ◽  
System A ◽  
Modeling Study

scholarly journals Accurate pH and O2 measurements from Spray underwater gliders

2020 ◽  
Author(s):  
Yuichiro Takeshita ◽  
Brent D. Jones ◽  
Kenneth S. Johnson ◽  
Francisco P. Chavez ◽  
Daniel L. Rudnick ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Dissolved Inorganic Carbon ◽  
Current System ◽  
Piecewise Linear ◽  
Ph Sensor ◽  
Saturation State ◽  
California Current System ◽  
Central California ◽  
Underwater Gliders ◽  
Better Than

AbstractThe California Current System is thought to be particularly vulnerable to ocean acidification, yet pH remains chronically undersampled along this coast, limiting our ability to assess the impacts of ocean acidification. To address this observational gap, we integrated the Deep-Sea-DuraFET, a solid state pH sensor onto a Spray underwater glider. Over the course of a year starting in April 2019, we conducted 7 missions in Central California, which spanned 161 glider days and >1600 dives to a maximum depth of 1000 m. The sensor accuracy was estimated to be ± 0.01 based on comparisons to discrete samples taken alongside the glider (n=105), and the precision was ± 0.0016. CO2 partial pressure, dissolved inorganic carbon, and aragonite saturation state could be estimated from the pH data with uncertainty better than ± 2.5%, ± 8 μmol kg-1, and ± 2%, respectively. The sensor was stable to ± 0.01 for the first nine months, but exhibited a drift of 0.015 during the last mission. The drift was correctable using a piecewise linear regression based on a reference pH field at 450 m estimated from published global empirical algorithms. These algorithms require accurate O2 as inputs, thus, protocols for a simple pre-deployment air-calibration which achieved accuracy of better than 1 % were implemented. The glider observations revealed upwelling of undersaturated waters with respect to aragonite to within 5 m below the surface near Monterey Bay. These observations highlight the importance of persistent observations through autonomous platforms in highly dynamic coastal environments.

scholarly journals Reconstruction of Diffusion Coefficients and Power Exponents from Single Lagrangian Trajectories

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 111
Author(s):  
Leonid M. Ivanov ◽  
Collins A. Collins ◽  
Tetyana Margolina
Keyword(s):  
Black Sea ◽  
Diffusion Coefficients ◽  
Current System ◽  
Mean Square Displacement ◽  
California Current ◽  
The Black Sea ◽  
Mean Square ◽  
California Current System ◽  
The Mean ◽  
Non Gaussian

Using discrete wavelets, a novel technique is developed to estimate turbulent diffusion coefficients and power exponents from single Lagrangian particle trajectories. The technique differs from the classical approach (Davis (1991)’s technique) because averaging over a statistical ensemble of the mean square displacement (<X2>) is replaced by averaging along a single Lagrangian trajectory X(t) = {X(t), Y(t)}. Metzler et al. (2014) have demonstrated that for an ergodic (for example, normal diffusion) flow, the mean square displacement is <X2> = limT→∞τX2(T,s), where τX2 (T, s) = 1/(T − s) ∫0T−s(X(t+Δt) − X(t))2 dt, T and s are observational and lag times but for weak non-ergodic (such as super-diffusion and sub-diffusion) flows <X2> = limT→∞≪τX2(T,s)≫, where ≪…≫ is some additional averaging. Numerical calculations for surface drifters in the Black Sea and isobaric RAFOS floats deployed at mid depths in the California Current system demonstrated that the reconstructed diffusion coefficients were smaller than those calculated by Davis (1991)’s technique. This difference is caused by the choice of the Lagrangian mean. The technique proposed here is applied to the analysis of Lagrangian motions in the Black Sea (horizontal diffusion coefficients varied from 105 to 106 cm2/s) and for the sub-diffusion of two RAFOS floats in the California Current system where power exponents varied from 0.65 to 0.72. RAFOS float motions were found to be strongly non-ergodic and non-Gaussian.

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