The larval stages of marine benthic organisms is an inherently vulnerable period in the life cycle due to the high risk of predation, food limitation, and the vagaries of ocean currents and chemistry, all processes that are critical determinants of recruitment to the adult population. Changes in recruitment year-to-year have implications for the structure of benthic communities, and in some cases, the fisheries that rely on them. Rapidly changing climate and pelagic food webs are shifting the timing and transport of planktonic larvae, altering interactions with prey, predators and competitors with implications for poleward range shifts. The aim of this session is to bring together researchers investigating the impact of climate change on larval dispersal, development, and trophic interactions. We hope to attract presentations based on laboratory studies, field work or models from a range of benthic taxa.
Lead Organizer: David Fields, Bigelow Labs for Ocean Sciences (dfields@bigelow.org)
Co-organizers:
Richard Wahle, University of Maine (richard.wahle@maine.edu)
Alexander (Alex) Ascher, University of Maine (alexander.ascher@maine.edu)
Rachel Lasley-Rasher, University of Southern Maine (rachel.lasleyrasher@maine.edu)
Presentations
10:30 AM
Phenology changes of the North Sea meroplankton since 1975 (5324)
Primary Presenter: Raquel Marques, Senckenberg am Meer (raquel.marques@senkenberg.de)
The North Sea is changing rapidly, driven by modifications in human activities and impacts of climate change. The reduction of nutrient loads from river discharges and the rising water temperatures act in synergy resulting in modifications on the phenology of marine organisms. Phenological changes have been described for several zooplankton species, but the full extension of their response has been only partially assessed, often ignoring the less abundant but ecologically and/or economically important species. This is particularly true for meroplankton organisms, for which the asynchrony between seasonal cycles of these larvae and their food might ultimately affect the recruitment of the adult benthic populations. Here we used a 46-years time series of meroplankton species (decapod larvae and gelatinous zooplankton), monitored at Helgoland Roads, to describe their long-term changes in phenology associated with modifications in the ecosystem. We used a combination of linear and non-linear statistical models to uncover (a)synchronous changes in the phenology of species and their environment, its drivers, and what impact they might have on the ecosystem. The results highlight that changes in phenology differed depending on the taxa, stressing the importance of considering species-specific ecology to understand interspecific relationships. This might have important implications for the benthic-pelagic coupling of meroplankton taxa, regulating the recruitment and, therefore, the composition of benthic communities, with possible significant ecological and socioeconomic effects.
10:45 AM
BRIDGING THE SPAWNER-RECRUIT DISCONNECT: LINKING GULF OF MAINE LOBSTER RECRUITMENT DYNAMICS TO REGIME SHIFTS IN THE PELAGIC FOOD WEB (7018)
Primary Presenter: Richard Wahle, University of Maine (richard.wahle@maine.edu)
The Gulf of Maine has historically supported some of the most productive lobster fishing grounds on earth. Over the past decade, however, a surprising disconnect has emerged between the burgeoning numbers of breeding lobster and declines in their young offspring recruiting to coastal nurseries. A recent correlative analysis suggests these declines in young lobsters may be linked to shrinking production of zooplankton, and in particular the energy-rich copepod <em>Calanus finmarchicus</em>, a foundational member of the Gulf’s zooplankton assemblage. Here we first provide a more comprehensive analysis of that correlation by drawing upon NOAA’s three-decade EcoMon zooplankton data time series to evaluate the spatial extent of trophic and other oceanographic correlates over the full area of the Gulf of Maine. Our findings suggest that the weakening influence of cold, nutrient rich, Labrador Slope Water and strengthening effects of warm, nutrient poor, Gulf Stream waters have precipitated an ecosystem-wide regime shift in the Gulf over the past decade that may have greater implications for lobster recruitment than previously suspected. This correlative analysis sets the stage for subsequent presentations in this session that provide a more mechanistic test of the hypothesis that larval lobster survival is limited by their planktonic food supply.
11:00 AM
Climate influence on American lobster reproductive ecology and larval connectivity along coastal New England (6780)
Primary Presenter: Andrew Goode, University of Maine (andrew.goode@maine.edu)
The New England Continental Shelf has warmed faster than 99% of the world’s ocean and sits along one of the largest latitudinal thermal gradients in the world, providing a natural laboratory to evaluate how rising temperatures affect the reproduction of marine species. We examined patterns of spawning and egg hatching of North America’s most valuable marine species, the American lobster (Homarus americanus), over the largest scale of any previous study by using unique multi-agency sampling programs, a novel analytical approach to egg development data, and simulated ocean conditions. Lobsters are remarkably adept at maintaining a consistent date at which spawn and egg hatch occur despite changes in ocean temperatures. However, elevated temperatures cause spawning and egg hatching to occur over shorter time frames, shifting the spawn and hatch season earlier at warmer locations and during warmer years. As the New England Continental Shelf continues to warm, these responses to rising temperatures could alter the phenology, dispersal, and connectivity of larval lobster populations affecting the productivity of this economically important species. This work highlights how organism life history processes can asymmetrically respond to climate change, necessitating a more in-depth understanding of how rising temperatures affect the interfaces between behavior, biological processes, and local oceanography.
11:15 AM
Diverging phenology of lobster larvae and their potential zooplankton prey in a warming ocean (7396)
Primary Presenter: Joshua Carloni, NH Fish and Game (joshua.t.carloni@wildlife.nh.gov)
We build on previous research describing correlative links between changes in the abundance of the copepod Calanus finmarchicus, a foundational zooplankton species of the pelagic food web, and diminishing recruitment of young-of-year lobster to benthic nurseries in the Gulf of Maine. First, we provide photographic evidence confirming that lobster larvae can handle and readily consume C. finmarchicus. Then, using parallel 31 year time series of lobster larvae and zooplankton collected on the New Hampshire coast between 1988 and 2018, we investigated how changes in phenology of stage I larval lobster and their putative copepod prey, Calanus finmarchicus, affects their temporal overlap and potential to interact. We found that over the time series both lobster egg hatch and the first appearance of larvae trended earlier in the season, a trend significantly correlated with ocean warming. The last appearance of larvae in late summer has been delayed, however, thereby extending the larval season. Even with the longer larval lobster season, the C. finmarchicus season has increasingly been ending before the peak abundance of stage I lobster larvae. The net effect is a widening mismatch in phenology of the two species, an outcome consistent with the hypothesis that changes in abundance and phenology of C. finmarchicus have contributed to recent declines in lobster recruitment.
11:30 AM
IMPLICATIONS OF A WARMING CLIMATE FOR LARVAL PRODUCTION AND TROPHIC INTERACTIONS OF THE AMERICAN LOBSTER (6906)
Primary Presenter: Alexander Ascher, University of Maine and Bigelow Laboratory for Ocean Sciences (ascher.alex@gmail.com)
The Gulf of Maine is warming faster than 99% of the world’s oceans. The changes have significant and predictable effects on its most iconic and commercially important species: the American lobster. As the water warms, lobsters become sexually mature earlier, leading to a decrease in the average size of ovigerous lobsters. Smaller females produce fewer, smaller embryos, which hatch into smaller larvae that are less capable of surviving starvation conditions. Concurrently, the rapid rise in temperature is driving a reorganization of zooplankton community structure and affecting the phenology of zooplankton populations. These changes may have important consequences for the feeding and survival of small, ill-equipped larvae. Our gut dissection and eDNA larval diet study shows that lobster larvae rely on abundant prey that are rich in essential fatty acids for normal development. However, key lipid rich copepods such as Calanus finmarchicus are undergoing temperature-related declines in abundance within the Gulf of Maine which heightens the risk that larvae are becoming food limited.
11:45 AM
OUTGROWING THE RISKS OF PLANKTONIC LIFE: ONTOGENY OF PREY PURSUIT, HANDLING AND INGESTION BY THE LARVAL AMERICAN LOBSTER (6907)
Primary Presenter: Evelyn Layland, University of Maine (evelyn.layland@maine.edu)
The American lobster (<em>Homarus americanus</em>) plays an integral role in the coastal Northwest Atlantic as a benthic consumer and the target of the most valuable single-species fishery in North America. In the past decade, benthic recruitment of juvenile lobster has declined, even as egg production has increased, suggesting heightening levels of larval mortality. Recent correlative studies in the Gulf of Maine further suggest early-stage larval survival may be related to the supply composition of planktonic foods. Despite these correlative studies and the economic importance of the species, relatively little is yet known about how larval lobsters interact with their prey in the pelagic environment. As development progresses through the four planktonic larval and postlarval stages, the young lobsters rely heavily upon zooplankton for food. During these early developmental stages, lobster larvae undergo significant morphological changes. This study used a combination of laboratory-based feeding experiments and video recordings to examine changes in feeding behavior and ingestion rates between larval stages. We observed dramatic stage-to-stage improvements in the capacity to pursue, capture, handle, and ingest specific prey, especially after the metamorphosis to the postlarval stage. The results highlight the vulnerability of the early life stages to low food densities. They also elucidated differences in the ability of specific prey taxa to evade predation. Quantifying the interactions between larval lobsters and their prey enhances our understanding of how larvae interact with the pelagic food web, the fraction of available zooplankton representing viable food sources, and how lobster larvae may be impacted by altered prey availability associated with climate change.
SS122 Vulnerability and Adaptation of Meroplankton Larvae in a Changing Climate
Description
Time: 10:30 AM
Date: 5/6/2023
Room: Sala Portixol 1