The U.S. Long Term Ecological Research (LTER) network expanded in 2017 to encompass four marine sites with a pelagic focus, complementing existing time-series maintained by NSF, NOAA, and multiple international funding agencies and enhancing our ability to document multidecadal ecosystem responses to climate variability and change across a global gradient. The four LTER sites span a range in terms of physical environment, geography, bathymetry, and terrestrial influence. Palmer LTER, on the western Antarctic Peninsula and extending 200 km offshore, is dominated by seasonal changes in sea ice cover and light availability. The California Current Ecosystem LTER is an eastern boundary upwelling regime and primarily an open ocean site with minor terrestrial inputs. The Northeast U.S. Shelf and Northern Gulf of Alaska LTER sites extend from the continental shelf into the open ocean, with significant terrestrial influences. All of the sites are associated with productive fisheries, and all are experiencing warming trends in surface air temperatures with associated impacts on mixed layer temperature and depth, and/or sea ice cover. This session will showcase ongoing studies of ecological responses at the LTER sites in terms of primary production, community composition and structure, carbon and nutrient cycling, and disturbance. We strongly encourage submissions related to these topics from other (non-LTER) national and international pelagic time-series sampling programs. Recent cross-LTER site synthesis efforts will also be highlighted.
Lead Organizer: Katherine Barbeau, Scripps Institution of Oceanography, UC San Diego (kbarbeau@ucsd.edu)
Co-organizers:
Russ Hopcroft, University of Alaska Fairbanks (rrhopcroft@alaska.edu)
Heidi Sosik, Woods Hole Oceanographic Institution (hsosik@whoi.edu)
Oscar Schofield, Rutgers University (oscar@marine.rutgers.edu)
Presentations
04:30 PM
Spatial and community synchrony of copepods in the Continuous Plankton Recorder Survey of the Western North Atlantic (9116)
Primary Presenter: Lawrence Sheppard, Marine Biological Association (lawshe@mba.ac.uk)
The Continuous Plankton Recorder Survey is a long-term monitoring effort using consistent methodology since 1958. Monthly data is available from routes running across the Western North Atlantic and along the NE US Continental Shelf, through the NES-LTER. Populations of large (all individuals counted) and small (semi-quantitative counts by sub-sampling) copepods exhibit both seasonal and longer term fluctuations. Due to dispersal and oceanographic Moran effects, the copepod populations exhibit various time-and-timescale-specific spatially synchronous features identified by ‘wavelet’ analysis. Positive and negative associations between the fluctuations of different taxa can be investigated using the wavelet approach, with consequences for the community characteristics of the copepods. Spatially synchronized, ‘in-phase’ relationships between locations and between taxa are characteristic of the seasonal productivity cycle, driving changes in total copepod numbers and total biovolume which are important to the food value of the copepods. Proportional in-phase changes in abundance of different taxa produce no change in other community characteristics such as alpha diversity or community size-spectral coefficients. Spatially unsynchronized changes produce changes in beta diversity at the relevant timescale, while maintaining average population stability at large spatial scales. Spatially synchronized, negatively associated changes in populations of large and small copepods can cause widespread changes in alpha diversity, size-spectral coefficients, and mean size of copepods.
04:45 PM
SECULAR TRENDS AND INTRINSIC VARIABILITY OF THE ZOOPLANKTON OF THE CALIFORNIA CURRENT ECOSYSTEM (9226)
Primary Presenter: Mark Ohman, Scripps Institution of Oceanography (mohman@ucsd.edu)
The emergence time of an underlying trend in a time series is directly related to the intrinsic variability of the property of interest. Most zooplankton populations show high variability on multiple scales, hence the emergence time is long, requiring decades of systematic sampling in order to detect underlying trends. Here we analyze the 75-year time series of mesozooplankton sampled by CalCOFI and analyzed taxonomically in the California Current Ecosystem (CCE) LTER site, supplemented by the 19-year time series of mesozooplankton analyzed by digital Zooscan, also by CCE-LTER. The data illustrate long-term secular changes in some taxa, but not in most, suggesting altered community structure that has implications for predator foraging success and C export. While the C biomass of total euphausiids has increased, this masks an important underlying distinction: mid-latitude euphausiids have increased, but low-latitude euphausiids have not, instead responding to low frequency variability dominated by the PDO. While appendicularians have increased progressively in C biomass over the past 7 decades, other pelagic tunicates have not. Pyrosomes irrupted in the Southern and Central California region in 2014, although such outbreaks previously waxed in the 1950s and 1960s and waned in the intervening decades. Evidence from the last 2 decades suggests a major increase in planktonic Rhizaria. The changes in the mesozooplankton of this major upwelling ecosystem do not correspond to expectations from a simple 1-D model of progressively increased ocean stratification.
05:00 PM
LONG-TERM CHANGES IN LARVAL GREY ROCKCOD: A POTENTIAL CLIMATE CHANGE “WINNER” IN THE WESTERN ANTARCTIC PENINSULA (9153)
Primary Presenter: Meredith Nolan, Virginia Institute of Marine Science (mnolan@vims.edu)
The western Antarctic Peninsula (WAP) is one of the fastest warming regions globally, leading to decreased sea ice coverage and increased ocean temperature. Many Antarctic fishes have specialized adaptations to survive freezing waters, and thus assumed to have low potential for adapting to a warmer ocean. However, species with physiological and environmental plasticity may experience improved survival and expanded livable ranges, making them climate change “winners” in the Southern Ocean. We used a 27-year time series from the Palmer Antarctica Long-Term Ecological Research (PAL LTER) program of length, abundance, and distributional data for the larvae of the Notothenioid Lepidonotothen squamifrons (grey rockcod) to examine their potential for adaptation and range expansion along the WAP. Information on the early life of grey rockcod is very limited, but physiological plasticity has been documented in adults. We show that since 1993, larval grey rockcod have shifted slightly poleward in mean latitude along the WAP. Our model results also show higher larval abundance and growth rate at higher temperatures. These findings suggest that grey rockcod have the potential for range expansion along the WAP. An adult diet analysis shows that one of their most important food sources are gelatinous salps, which have shown a similar ability to tolerate warmer conditions. These results are some of the first to document a potentially favorable response of fishes endemic to the Southern Ocean to continued warming, helping us envisage the future of this marine pelagic ecosystem.
05:15 PM
Decadal Ocean Soundscapes Reveal Biological, Climatic, and Economic Fluctuations (9603)
Primary Presenter: Natalie Posdaljian, UC San Diego (nposdalj@ucsd.edu)
Decadal variations of ocean soundscapes are closely linked to large-scale climatic and economic fluctuations. Our study revealed that sound levels associated with biological and ambient sound sources varied seasonally and correlated with large-scale climatic patterns and long-term oceanographic fluctuations. For instance, during marine heatwaves, baleen whale sound levels decreased in southern sites and increased in northern sites adjacent to the California Current. Ship sound levels at high-traffic sites reflected economic events such as recessions, labor shortages and negotiations, and changes to port activities. For this analysis we analyzed acoustic recordings spanning over a decade at each of six sites within the Southern California Bight to investigate the interannual, seasonal, and diel patterns. By examining acoustic energy from fin and blue whales along with ambient sound sources like ships and wind, we identified the changes in soundscape over time and space. Marine soundscapes offer an approach to assessing the ocean's condition amid ongoing climatic and economic fluctuations.
05:30 PM
Seasonal predictability in coastal planktonic communities (8804)
Primary Presenter: Miraflor Santos, Woods Hole Oceanographic Institution (msantos@whoi.edu)
Predictive understanding of variability in planktonic communities could improve ecosystem response forecasts. We studied predictability in observations from a nearshore coastal site (Martha’s Vineyard Coastal Observatory) where long-term (>15 y) high-frequency observations with automated flow cytometry and imaging allow many genera and species of phytoplankton and microzooplankton to be separately quantified. Wavelet analysis emphasized that the annual time scale dominates variability for most taxa (>70% display annual periodicity in all years observed). To further examine seasonal predictability, we quantified interannual variability from several angles for each taxon: consistency in the shape of the annual cycle; shifts in seasonal cycle timing; changes in seasonal cycle amplitude; and contributions of constancy versus contingency on time of year. We used a combination of a novel cyclicity index, Colwell’s predictability indices, and a lag-adjusted seasonal model that incorporates seasonally resolved timing and amplitude fluctuations. Our findings reveal significant variability in the degree of predictability and identify the most predictable and least predictable members of the community. We find that shifts in amplitude are particularly important in driving overall variability and that the dynamics of many species or genera are more predictable than their aggregated functional or taxonomic group (e.g., particular diatoms compared to all diatoms combined). Our results underscore the importance of accounting for taxon-specific dynamics when modeling planktonic ecosystems.
05:45 PM
MODELS EXPLAINING LONG-TERM PARTICLE EXPORT AT 150 M DEPTH AT STATION ALOHA (9470)
Primary Presenter: Robert Hall, University of Montana (bob.hall@flbs.umt.edu)
Organic particles settling from the surface ocean provide the fuel for enhanced deep-ocean carbon storage, often termed the "biological pump." Small variations in the fraction of primary production that is exported can have large effects on the global carbon cycle. 33y of measured particle export at a depth of 150 m at Station ALOHA in the North Pacific Subtropical Gyre show a clear long-term increase in measured rates of primary production, but no long-term change in export flux, and temporal variation in flux was uncoupled from primary production. Understanding the controls on this flux variation is needed to enable future predictions. Depth-integrated primary production only weakly predicted particle flux, explaining only 10% of the variation in flux with no lagged effects at monthly time scales. Other measured properties, e.g., chlorophyll and particle volume distribution, did not improve the explanatory power. Among-trap deployment error was high; export flux variation measured over short time scales via separate sediment trap deployments showed variation that is 50% of the temporal variation in the time series data, indicating an upper predictive limit of 50%. Simple process-based models of particle settling velocity show large sensitivity to flux based on small variations in settling velocity and particle mineralization rate. Understanding controls on short time-scale (i.e., monthly) variation in particle flux remains elusive, and here we show that combined process and statistical models are needed to understand these controls at various time scales.
SS27B - Long-term perspectives in marine pelagic ecosystem research
Description
Time: 4:30 PM
Date: 30/3/2025
Room: W207AB