Showing 1 - 10 of 11 Items

• Embargo End Date: 2029-05-16

Date: 2024-01-01

Creator: Nicholas Takaki Tienhui Yoong

Access: Embargoed

• Embargo End Date: 2027-05-16

Date: 2024-01-01

Creator: Everett Horch

Access: Embargoed

Date: 2023-01-01

Creator: S. Maria Garcia

Access: Open access

Non-native species foundation species can alter ecosystems in both positive and negative ways. The creation of habitat can be beneficial to native species when they provide a limiting resource or in a stressful environment. Yet this creation of habitat can also be detrimental by replacing native species and/or facilitating the presence of more non-native species. In Willapa Bay, WA, a non-native foundation species, Zostera japonica, co-exists with the native foundation species Zostera marina. Zostera japonica persists at the higher intertidal in monocultures, the two species overlap in the mid intertidal, and Z. marina persists in monocultures in the low intertidal. Epifaunal invertebrates, the organisms that live on eelgrass blades, connect eelgrass to higher trophic levels. Through a series of transplants and removals, I used this zonation pattern to ask if the two species can fulfill a similar functional role in respect to epifaunal invertebrates (functional redundancy), and if this was due to the identity of the foundation species or a response to the stress gradient of the intertidal. My results suggest that the epifaunal invertebrate community is responding more to the physiological stress gradient, and the functional redundancy of the two species depends on the location they are found. Z. japonica is expanding the range of vegetated habitat into to the physiologically stressful high zone, which supports a different community. This experiment highlights that the impacts of non- native species are highly localized and that abiotic and biotic factors are important to trophic interactions.

Date: 2021-01-01

Creator: Hannah L. Randazzo

Access: Open access

Anthropogenic CO2 is changing the pCO2, temperature, and carbonate chemistry of seawater. These processes are termed ocean acidification (OA) and ocean warming. Previous studies suggest two opposing hypotheses for the way in which marine climate stress will influence echinoderm calcification, metabolic efficiency, and reproduction: either an additive or synergistic effect. Sea stars have a regenerative capacity, which may be particularly affected while rebuilding calcium carbonate arm structures, leading to changes in arm growth and calcification. In this study, Asterias forbesi were exposed to ocean water of either ambient, high temperature, high pCO2, or high temperature and high pCO2 for 60 days, and the regeneration length of the amputated arm was measured weekly. Ocean acidification conditions (pCO2 ~1180 μatm) had a negative impact on regenerated arm length, and an increase in temperature of +4°C above ambient conditions (Fall, Southern Gulf of Maine) had a positive effect on regenerated arm length, but the additive effects of these two factors resulted in smaller regenerated arms compared to ambient conditions. Sea stars regenerating under high pCO2 exhibited a lower proportion of calcified mass, which could be the result of a more energetically demanding calcification process associated with marine climate stress. These results indicate that A. forbesi calcification is sensitive to increasing pCO2, and that climate change will have an overall net negative effect on sea star arm regeneration. Such effects could translate into lower predation rates by a key consumer in the temperate rocky intertidal of North America.

• Embargo End Date: 2028-05-18

Date: 2023-01-01

Creator: Olivia Bronzo-Munich

Access: Embargoed

Date: 2023-01-01

Creator: Kellie Navarro

Access: Open access

The coral Astrangia poculata inhabits hard-bottom environments from the Gulf of Mexico to Massachusetts and withstands large seasonal variation in temperature (–2 to 26 °C). This thermal range and its ability to live in a facultative symbiosis makes this species an ideal model system for investigating stress responses to ocean temperature variation. Although it has been shown that aposymbiotic A. poculata upregulates more genes in response to cold stress than heat stress, the transcriptomic response of the holobiont (coral host and symbiotic algae) to stress is unknown. In this study, we characterize changes in gene expression in both the host and symbionts under cold stress (6ºC) and ambient (12ºC) seawater temperatures. We use RNAseq to visualize how patterns of global gene expression change in response to these temperatures within the transcriptomes of replicate corals (n=10, each temperature) and their symbiont partners. By filtering the holobiont assembly for known coral host and symbiont genes, we contrasted patterns of differential expression (DE) for each partner and the functional processes for each set of DE genes. Differential gene expression analyses revealed that the cnidarian coral host responds strongly to cold stress, while algal symbionts did not have a significant stress response. In the coral host, we found up-regulation of biological processes associated with DNA repair, immunity, and maintaining cellular homeostasis as well as downregulation of mechanisms associated with DNA repair and RNA splicing, indicating inhibition of necessary cellular processes due to environmental stress.

Date: 2000-01-01

Creator: Nalini M. Nadkarni, Nathaniel T. Wheelwright

Access: Open access

The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. Featuring synthetic chapters and specific accounts written by more than 100 biologists and local residents, the 573-page book documents in a single volume everything known about the biological diversity of Monteverde, Costa Rica, and how to protect it. New short chapters which update and expand the research presented in the 2000 Oxford publication were written in 2014 and are now available.

Date: 2020-01-01

Creator: James L. O'Shea

Access: Access restricted to the Bowdoin Community

Date: 2024-01-01

Creator: Mary Alta Rogalski, Elizabeth S Baker, Clara M Benadon

Access: Open access

Increasing application of road deicing agents (e.g., NaCl) has caused widespread salinization of freshwater environments. Chronic exposure to toxic NaCl levels can impact freshwater biota at genome to ecosystem scales, yet the degree of harm caused by road salt pollution is likely to vary among habitats and populations. The background ion chemistry of freshwater environments may strongly impact NaCl toxicity, with greater harm occurring in ion-poor, soft water conditions. In addition, populations exposed to salinization may evolve increased NaCl tolerance. Notably, if organisms are adapted to their natal lake water chemistry, toxicity responses may also vary among populations in a given test medium. We examined how this evolutionary and environmental context may interact in shaping NaCl toxicity with a pair of laboratory reciprocal transplant toxicity experiments, using natural populations of the water flea Daphnia ambigua from three lakes differing in ion availability. The lake water environment strongly influenced NaCl toxicity in both trials. NaCl greatly reduced reproduction and r in lake water from a low-ion/ calcium-poor environment compared with water from both a calcium-rich lake and an ion-rich coastal lake. Daphnia from this coastal lake were most robust to the effects of NaCl. A significant population x environment interaction shaped survival in both trials, suggesting that local adaptation to the test waters used contributed to toxicity responses. Our findings that the lake water environment, adaptation to that environment, and adaptation to a focal contaminant may shape toxicity demonstrate the importance of considering environmental and biological complexity in mitigating pollution impacts.

Date: 2021-01-01

Creator: Sophia Walton

Access: Open access

The blue mussel Mytilus edulis alters its phenotype in species-specific ways in response to either green crab (Carcinus maenus) or sea star (Asterias sp.) predation. Previous studies have shown that only sea stars induce changes in abductor muscle morphology, while green crabs generally alter the shape and thickness of shells. In the Western Gulf of Maine, Blue mussels collected from wave protected sites with abundant green crab predators were shown to have significantly thicker shells and larger adductor muscles than mussels collected from wave exposed sites with few green crab predators. The phenotypes of mussels originating from wave-protected and high green crab abundance sites increased the handling time by A. forbesi compared to sites with low wave exposure and high green crab abundance. These results contradict the paradigm that shell thickness trades off with abductor morphology, and I propose that a likely candidate for increased energy allocation to these traits is a decrease in reproductive allocation. My results further suggest that the escalating “arms race” between invasive green crabs and blue mussels in the Western Gulf of Maine is leading to changes in the phenotypic response of mussel populations in ways that are likely impacting sea star foraging dynamics.