Embedded Files
Current Research
Current Research
Planktonic to sessile: drivers of spatial and temporal variability across barnacle life stages and indirect effects of the Pacific Marine Heatwave
Planktonic to sessile: drivers of spatial and temporal variability across barnacle life stages and indirect effects of the Pacific Marine Heatwave
Traiger et al. (2024) Journal of Plankton Research https://doi.org/10.1093/plankt/fbae059
Check out the 4 minute segment aired on Kachemak Currents.
Check out my interview on Six Minute Science (episode 19).
Barnacles are a foundation species in intertidal habitats. During the Pacific Marine Heatwave (PMH), intertidal barnacle cover increased in the northern Gulf of Alaska (GoA); however, the role of pelagic larval supply in this increase was unknown. Using long-term monitoring data on intertidal benthic (percent cover) and pelagic larval populations (nauplii and cyprid concentrations), we examined potential environmental drivers (temperature, chlorophyll-a, mixed layer depth) of larval concentration and whether including larval concentration at regional and annual scales improved intertidal barnacle percent cover models in two study regions in the GoA. In both regions, larval concentrations were slightly higher following the PMH. Percent cover models were improved by including cyprid concentrations (but not nauplii), and the effect strength varied by site and tidal elevation. This indicates that larval concentration contributes as a bottom–up driver of benthic barnacle abundance. There is little evidence of a direct effect of the PMH on either life stage. Instead, our results may illustrate the positive feedback between life stages, where higher adult benthic abundance increased larval concentrations, which then supplied more new recruits to the benthos. As heatwaves continue to occur, integrating various data types can provide insights into factors influencing both benthic and pelagic communities.
A decade of death and other dynamics: Deepening perspectives on the diversity and distribution of sea stars and wasting
A decade of death and other dynamics: Deepening perspectives on the diversity and distribution of sea stars and wasting
This article describes the effects of the sea star wasting epidemic on sea star populations across the eastern Pacific over the last decade. We synthesized long term monitoring data from six research programs from Mexico to Alaska. The timeline and intensity of sea star wasting was described by latitude and hypotheses about physical factors driving sea star wasting were tested. Out of 65 sea star species examined, about 12 species were clearly impacted by sea star wasting. Elevated sea surface temperature and low wave exposure, and freshwater discharge in the north, were associated with the sea star wasting outbreak. These findings are important because 1) understanding which abiotic factors drive sea star wasting could help with predicting future outbreaks and 2) understanding baseline prevalence of sea star wasting will assist monitoring programs in detecting the start of new outbreaks.
Photo: Brenda Konar
Lack of strong responses to the Pacific marine heatwave by benthivorous marine birds indicates importance of trophic drivers
Lack of strong responses to the Pacific marine heatwave by benthivorous marine birds indicates importance of trophic drivers
Robinson B, HA Coletti, B Ballachey, JL Bodkin, K Kloecker, SB Traiger, D Esler (2023) Lack of strong responses to the Pacific marine heatwave by benthivorous marine birds indicates importance of trophic drivers. Marine Ecology Progress Series https://doi.org/10.3354/meps14384
The Pacific marine heatwave (PMH) of 2014-2016 was an intense, long-lasting environmental disturbance expressed throughout the north Pacific. While dramatic consequences of the PMH on pelagic food webs have been well documented, effects on nearshore food webs, i.e., those based on macroalgae primary productivity, benthic invertebrate intermediate consumers, and specialized benthivorous top predators including some marine birds, are not well understood. We conducted summer and winter coastline marine bird surveys in two National Parks in the northern Gulf of Alaska from 2006 – 2022. We evaluated changes in abundance of benthivorous marine birds in relation to the heatwave, after accounting for effects of season and region. We also evaluated changes in abundance of nearshore benthic invertebrate prey to allow specific consideration of a prey-based mechanism for effects of the PMH across food webs. We found that benthivorous marine birds, consisting of sea ducks and shorebirds, did not show a strong response to the PMH, unlike significant effects demonstrated by piscivorous birds in pelagic biomes. In contrast to extreme reductions in quantity and quality of forage fish documented elsewhere, we found that common benthic invertebrate prey abundance remained relatively stable. Our results support the hypothesis that, across food webs, top predator responses to the PMH were driven primarily by how and whether the PMH affected their prey availability. These findings show how a large-scale environmental perturbation affects biological communities differently through various trophic pathways, which provides insight into ecosystem resiliency and can inform management strategies in the face of persistent climate change.
Effects of sea star wasting on blue mussels
Effects of sea star wasting on blue mussels
Mussels occupy a key middle trophic position in nearshore food webs linking primary producers to predators. Climate- related environmental changes may synergistically combine with changes in predator abundance to affect intertidal ecosystems. We ex- amined the influence of two major events on mussel (Mytilus trossulus) abundance in the northern Gulf of Alaska: the recent Pacific marine heatwave (PMH, 2014– 2016) and an outbreak of sea star wasting (SSW). We investigated how mussel abundance changed since the onset of SSW and whether the density of predatory sea stars or PMH- related temperature metrics explain variation in mussel abundance. Sea stars and mussels were surveyed since 2005 approximately annually in four regions of the northern Gulf of Alaska: Katmai (KATM), Kachemak Bay (KBAY), Kenai Fjords (KEFJ) and western Prince William Sound (WPWS). Mussel percent cover in the mid- intertidal increased 1– 3 years after declines in sea stars at all regions and in the low- intertidal at KATM, KBAY, and KEFJ, but not at WPWS. After the onset of SSW, large (≥20 mm length) mussel density and mussel bed width increased at KATM but not the other regions. Total mussel densities, including recruits, did not differ before and after the onset of SSW. The total number of sea stars significantly explained variation in mussel metrics, but the proportions of the three sea star species examined did not. We did not find strong evidence for direct effects of temperature on mussels. The effects of the PMH and the SSW outbreak appear to have combined, with increased tem- peratures indirectly benefiting mussels in concert with relaxed top- down pressure from sea stars, allowing for increased mussel abundance. Changing mussel abundance may affect intertidal local productivity and the abundance or performance of other nearshore consumers of mussels.
Past Research
Past Research
Limited biogeochemical modification of surface waters by kelp forest canopies: Influence of kelp metabolism and site-specific hydrodynamics
Limited biogeochemical modification of surface waters by kelp forest canopies: Influence of kelp metabolism and site-specific hydrodynamics
Climate change is causing decreases in pH and dissolved oxygen (DO) in coastal ecosystems. Canopy-forming giant kelp can locally increase DO and pH through photosynthesis, with the most pronounced effect expected in surface waters where the bulk of kelp biomass resides. However, limited observations are available from waters in canopies and measurements at depth show limited potential of giant kelp to ameliorate chemical conditions. We quantified spatiotemporal variability of surface biogeochemistry and assessed the role of biological and physical drivers in pH and DO modification at two locations differing in hydrodynamics inside and outside of two kelp forests in Monterey Bay, California in summer 2019. pH, DO, dissolved inorganic carbon (DIC), and temperature were measured at and near the surface, in conjunction with physical parameters (currents and pressure), nutrients, and metrics of phytoplankton and kelp biological processes. DO and pH were highest, with lower DIC, at the sur- face inside kelp forests. However, differences inside vs. outside of kelp forests were small (DO 6–8%, pH 0.05 higher in kelp). The kelp forest with lower significant wave height and slower currents had greater modification of surface biogeochemistry as indicated by larger diel variation and slightly higher mean DO and pH, despite lower kelp growth rates. Differences between kelp forests and offshore areas were not driven by nutrients or phytoplankton. Although kelp had clear effects on biogeochemistry, which were modulated by hydrodynamics, the small magnitude and spatial extent of the effect limits the potential of kelp forests to mitigate acidification and hypoxia.
Green sea urchin grazing under elevated temperature and sedimentation in Alaska
Green sea urchin grazing under elevated temperature and sedimentation in Alaska
Sea urchin grazing rates can impact kelp bed persistence. Elevated water temperature associated with climate change may increase grazing rates; however, these effects may interact with local stressors such as sedimentation. In Alaska, glacial melt is increasing with climate change and is resulting in higher sedimentation rates. The short-term effects of elevated temperature and sediment on grazing were investigated for the green sea urchin, Strongylocentrotus droebachiensis, in Kachemak Bay, Alaska. Feeding assays were conducted at ambient temperature and at 14 °C with no sediment controls and a high sediment treatment. Grazing rate significantly decreased in the presence of sediment but was not significantly affected by temperature. Along with sediment impacts on settlement and post-settlement survival, grazing inhibition may contribute to the commonly observed pattern of decreased macroinvertebrate grazer abundance in areas of high sedimentation. Increased sedimentation in the future may alter top-down control in kelp bed systems.
How will future sea temperature and sediment load affect grazing on kelp by New Zealand sea urchins?
How will future sea temperature and sediment load affect grazing on kelp by New Zealand sea urchins?
In summer 2017 I visited the University of Auckland Leigh Marine Laboratory as part of the NSF East Asia and Pacific Summer Institute Fellowship. Like many areas, sea temperatures are expected to rise in New Zealand with climate change. At the same time, sedimentation to the nearshore may increase with changes to land use, precipitation, and soil erosion. I conducted a lab experiment to determine the effect of these factors on grazing rates of the New Zealand sea urchin, Evechinus chloroticus and the black sea urchin, Centrostephanus rodgersii. Contrary to my expectation, I did not observe significant effects of elevated temperature of sedimentation on grazing rates of either species. These species may be tolerant of high sediment in their adult stage.
Effects of glacial melt on kelp recruitment and community development
Effects of glacial melt on kelp recruitment and community development
The assembly and maintenance of biological communities is influenced by environmental factors, which are predicted to shift with climate change. Glaciers are melting at increasing rates, delivering sediment and fresh water to coastal habitats. We hypothesized that environmental factors related to glacial discharge would be correlated to the initial recruitment and colonization of sessile communities in kelp beds, and to the abundance of mobile epibenthic invertebrates and adult kelp. To test these hypotheses, cleared rocks were placed at six sites at 10-m depth across a gradient of glacial-influence in Kachemak Bay, Alaska and the percent cover of the initial recruitment and the subsequent progression of the sessile community was monitored over 18 months. Small mobile invertebrates (such as limpets and chitons) were also monitored on these rocks for 18 months. Lastly, larger invertebrates (such as sea stars) and adult kelp were surveyed over the same time period along transects in the immediate vicinity of the cleared rocks. Environmental factors (sedimentation rates, salinity, temperature, irradiance, and nutrient concentration) were concurrently monitored at each site. Recruitment and subsequent colonization varied along the glacial gradient. At sites with higher sedimentation rates, recruitment and the subsequent developing community was dominated by barnacles with little or no kelp recruits and other macroalgae and high temporal variation in availability of bare space. At more oceanic sites, these communities were characterized by a slow increase in cover of encrusting and upright macroalgae, also with high variability among sites. Mobile invertebrates and adult kelp were more abundant at oceanic sites than the glacial sites. Using distance-based linear models, inorganic sedimentation rate was correlated to patterns of kelp bed recruitment and colonization and to the abundance of mobile invertebrates and adult kelps in the surrounding area. Changes in inorganic sedimentation with climate change may alter how kelp beds are distributed and structured in glacial estuaries.
Kelp microscopic stages and glacial melt
Kelp microscopic stages and glacial melt
High latitude kelp beds may be at risk from increasing sedimentation rates due to glacial melt. The sporophyte Nereocystis luetkeana (canopy-forming) occurs infrequently downstream of glacial melt where thick layers of sediment accumulate, while sporophytes of Saccharina latissima (understory) are common in these areas. We examined whether glacial melt conditions affect adult fecundity of either species, how sedimentation affects early gametophyte survival and growth, and whether gametophyte competitive interactions are altered by the presence of sediment. Fecundity did not differ in relation to glacial discharge for either species. In single species treatments, there was an effect of sediment on gametophyte survival but not growth for both species. In mixed species treatments when no sediment was added, N. luetkeana had higher survival than S. latissima when N. luetkeana was settled first. When sediment was added, S. latissima had higher survival than N. luetkeana when S. latissima was settled first. There was no difference in gametophyte growth between the two species for any treatment. Settlement timing may explain Nereocystis’ ability to coexist with Saccharina and to occur in some locations downstream of glacial discharge. Climate change could result in the loss of N. luetkeana by favoring S. latissima gametophytes in competitive interactions. This research made up the second chapter of my PhD dissertation.
Aleutian islands biodiversity
Aleutian islands biodiversity
Biogeographic breaks are often described as locations where a large number of species reach their geographic range limits. Samalga Pass, in the eastern Aleutian Archipelago, is a known biogeographic break for the spatial distribution of several species of offshore-pelagic communities, including numerous species of cold-water corals, zooplankton, fish, marine mammals, and seabirds. However, it remains unclear whether Samalga Pass also serves as a biogeographic break for nearshore benthic communities. In this study, we examined if the biogeographic break for offshore-pelagic communities applies to nearshore kelp forests by comparing abundance, biomass and percent bottom cover of species associated with kelp forests on either side of the pass. We observed marked differences in kelp forest community structure, with some species reaching their geographic range limits on the opposing sides of the pass. In particular, the habitat-forming kelp Nereocystis luetkeana, and the predatory sea stars Pycnopodia helianthoides and Orthasterias koelheri all occurred on the eastern side of Samalga Pass but were not observed west of the pass. In contrast, the sea star Leptasterias camtschatica dispar was observed only on the western side of the pass. We also observed differences in overall abundance and biomass of numerous associated fish, invertebrate and macroalgal species on opposing sides of the pass. We conclude that Samalga Pass is important biogeographic break for kelp forest communities in the Aleutian Archipelago and may demark the geographic range limits of several ecologically important species.
Foraging pits and shell litter as indicators of clam predators
Foraging pits and shell litter as indicators of clam predators
Poster presentation, Alaska Marine Science Symposium 2016
Hard substrate can limit kelp distribution, especially in areas of Alaska where glacial sediment covers rocks. I studied sea otter and sea star foraging on clams as sources of hard substrate for kelp colonization using surveys and in situ experiments to show that the excavations made by either species during their foraging cannot be distinguished, but that clam shell remains can be attributed to a predator with better certainty. This work showed that sea stars consume more clams than previously assumed, which has implications for the role of these predators in providing hard substrate for kelp colonization. This research made up the third chapter of my PhD dissertation.
Multiple approaches to assessing the effectiveness of marine reserves using the commercial sea cucumber Parastichopus parvimensis
Multiple approaches to assessing the effectiveness of marine reserves using the commercial sea cucumber Parastichopus parvimensis
The warty sea cucumber, Parastichopus parvimensis, has declined in some areas at the California Channel Islands since a dive fishery began in the 1990s. We evaluated the effectiveness of four reserves established in 2003 for P. parvimensis density. Annual P. parvimensis densities were collected during SCUBA surveys as part of Channel Islands National Park’s long-term kelp forest monitoring program. One-way ANOVAs and before-after, control impact (BACI) analyses to evaluate marine reserve effectiveness. P. parvimensis density was higher at three reserves than fished sites. BACI analysis could only be conducted for two reserves and showed significantly higher P. parvimensis density at one reserve. There were no increasing or decreasing trends at Santa Rosa Island, where fishing pressure for P. parvimensis is low. Parastichopus parvimensis is a model species of the importance of monitoring before MPAs and/or fisheries are established and the importance of long-term monitoring.
Invasive lionfish in South Caicos, Turks and Caicos Islands
Invasive lionfish in South Caicos, Turks and Caicos Islands
Poster presentation, Gulf and Caribbean Fisheries Institute Conference, 2011
Lionfish (Pterois volitans) were first observed at the island of South Caicos in 2007 and quickly spread to occupy every marine habitat. In 2010 I collected lionfish on deep reef to assess their size and depth distribution in South Caicos. Lionfish density was higher and average length was significantly larger on deep reefs than shallow habitats.
Community effects of an invasive bryozoan in the Monterey harbor
Community effects of an invasive bryozoan in the Monterey harbor
Poster presentation, UC Santa Cruz Undergraduate Research Symposium, 2010
Invasive species are a conservation concern because they often change the ecological communities they invade. Invasive species can compete with or prey on native species, or alter the structure of the habitat (ecosystem engineers). The invasive bryozoan Watersipora subtorquata, is abundant in the Monterey harbor and has been sighted in kelp forests in the Monterey Bay. I examined whether there is evidence that Watersipora has affected the “fouling community”, i.e. sessile invertebrates and algae that inhabit man-made structures, by studying the differences between photoquadrats with various levels of Watersipora cover. Corynactis californica negatively responded to increasing abundance (percent cover) of Watersipora, while Membranipora fusca positively responded. Diplosoma listerianum had high percent cover when there was high cover of Watersipora and when Watersipora was low or absent, but D. listerianum was much less abundant at moderate levels of Watersipora. These results suggest that Watersipora influences this fouling community because of the differences between the communities with different levels of Watersipora. However, experimental manipulations of the community would be necessary to confirm that Watersipora is the cause of these differences. I conducted this research for my senior thesis at the University of California, Santa Cruz.
Google Sites
Report abuse