Wednesday at 2:00 pm in Kuykendall 305

Zoom Link
Meeting ID: 838 4294 6028
Passcode: MBIOS25

“Investigating Forms of Plasticity in Three Echnoid Species from the Tropical North Pacific“
Date: 04/30
Speaker: Ethan Nash
Marine Biology MS student

Phenotypic plasticity allows marine invertebrate larvae to adjust morphology and development in response to environmental variability, but its expression across species and environmental gradients remains incompletely understood. We examined morphological plasticity in larvae of three tropical echinoids—Tripneustes gratilla, Echinometra mathaei, and Colobocentrotus atratus—reared under nine combinations of temperature (23, 26, 29 °C) and food concentration (200, 1000, 5500 algal cells mL⁻¹). Across seven experiments and six larval cohorts, we quantified post-oral arm length (POL), stomach length (SL), and median body length (MBL). Tripneustes gratilla displayed consistent morphological plasticity across spawns, with medium-food treatments producing the longest relative POL and high-food treatments promoting longer SL. Echinometra mathaei exhibited minimal POL plasticity in two spawns while C. atratus showed traditional plasticity with the lowest food treatments producing the longest POL relative to body size in a single spawn. For T. gratilla, tracked time to metamorphic competence and beaker larval duration for and larval duration (BLD) in a single spawn. Developmental timing was highly plastic in T. gratilla: at 29 °C with high food, larvae reached metamorphosis in ~25 days, while some medium-food larvae at 23 °C remained free-swimming after 366 days. Morphological plasticity was predominantly food-driven, with limited interaction effects from temperature. Larval duration was significantly affected by food availability, temperature, and their interaction in T. gratilla. These results show species-specific patterns of larval flexibility and suggest that morphology and larval duration is an environmentally responsive trait. Such plasticity may have important implications for dispersal, connectivity, and resilience under changing ocean conditions.

Friday at 1:30 pm in HIG 110

Zoom Link
Meeting ID: 849 8733 3061
Passcode: Retno25

“Nesting Ecology of Leatherback Turtle (Dermochelys coriacea) on Buru Island, Maluku, Indonesia”
Date: 05/02
Speaker: Retno Kusuma Ningrum
Marine Biology MS student

Leatherback turtles (Dermochelys coriacea) face significant conservation challenges due to global population declines and their susceptibility to both environmental and anthropogenic pressures. Fine-scale, site-specific research is critical for understanding population characteristics and developing effective conservation strategies. This study uses beach monitoring data collected over eight years (2017-2024), along with beach characteristic survey data from 2024, to examine the nesting behavior of leatherback turtles, beach characteristics, hatchling production, impacts of seasonality, and threats to eggs at Fena Leisela beach, Buru Island, Indonesia.

With over 1434 recorded nests and 178 unique individuals identified, findings show that leatherbacks typically lay five  clutches per season, with internesting intervals ranging from 9 to 12 days and a remigration interval of approximately 2-4 years. Based on the number of nests and estimated clutches per female, it is estimated that around 36 females nest annually at Fena Leisela beach. Nesting occurs  year-round, following a bimodal pattern with two peaks: June-July (dry season) and December-March (rainy season). Nesting activity has increased annually over the last eight years, likely due to the cessation of meat harvesting in 2017, which has allowed more turtles to complete their nesting cycles. However, a declining trend has been observed during the rainy season, suggesting increased pressures during this period.

The combination of beach monitoring and beach characteristic data in 2024 reveals that artificial lighting, slopes, and beach width are important cues in selecting nest sites. Leatherbacks predominantly nest in areas with minimal artificial light, moderate beach widths (approximately 14.2-26.1 meters), slopes ranging from 11.32% to 15.48%, diggable sand, and sparse vegetation cover. These findings suggest that leatherbacks exhibit specific preferences for nesting habitats. Interestingly, a few  individuals were observed nesting in well-lit areas, indicating that some turtles may tolerate a degree of disturbance.This study also highlights  a significant reduction in egg harvesting and predation, largely due to active beach monitoring and increased community awareness efforts involving local citizens, government officials, and traditional and religious leaders. Nests in high-risk areas (“doomed nests”) were relocated, resulting in the successful release of approximately 5,674 hatchlings. However, the hatching and emergence success rates were lower in relocated nests (F(1,671)=3.364, P=0.06 and F(1,671)=4.187, P=0.04, respectively), possibly due to changes in nest conditions such as moisture and temperature. Despite this, seasonal variation did not appear to negatively impact relocated nests, suggesting that nest relocation may be most effective during the rainy season, when the risk to nests is the highest. These findings offer valuable insight into the nesting ecology of leatherback turtles at Fena Leisela beach and provide a strong foundation for future research and the development of site-specific conservation strategies.

Wednesday at 11:00 am in Hamilton 203 

Zoom Link
Meeting ID: 849 4311 6008
Passcode: MBSP25

“Who are you calling a shrimp? Evaluating aggression, boldness, territoriality, and behavioral strategies in an invasive stomatopod (Gonodactylaceus falcatus)”
Date: 04/16
Speaker: Sophia Hanscom
Marine Biology Graduate Program MS student

Biological surveys conducted on Oʻahu, Hawaiʻi have indicated the stomatopod (Order  Stomatopoda), Gonodactylaceus falcatus, to be the most widely distributed invasive marine  invertebrate in nearshore marine ecosystems. Similar to marine crustaceans around the world, G. falcatus was introduced to Hawaiʻi due to the combination of increased maritime activity  following WWII and their planktonic larval phase. While this pathway has been documented for  facilitating its introduction into the islands, it remains unclear what characteristics have  supported the establishment and successful invasion of this species into this non-native  environment. Previous work has focused on the role behavior can play in this scenario,  suggesting that differences in specific behavioral traits between invasive and native species  contribute to the invasion success and overall interactions between these species and their new  environment. In particular, studies have identified behavioral syndromes (consistency of single  behavior across contexts and/or correlation between two traits) as a behavioral strategy that has  contributed to the invasion success of many taxa. I tested the boldness and aggression of G.  falcatus (n = 101) to determine if a behavioral syndrome was present and to characterize the  overall behavioral variation within these traits. Three syndrome analyses were conducted (mixed  model, intraclass correlation coefficient, Spearman’s correlation) and a lack of evidence for a  behavioral syndrome in this species was identified. While a syndrome wasn’t present, these  behavioral traits may still be contributing to their success if as a species they are more bold  and/or aggressive than the native stomatopod species. When analyzing the individual traits,  boldness and aggression increased across trial number (replicate) and this study also found larger  individuals to respond more aggressively than smaller counterparts. Some factors typically found  to impact how bold or aggressive an individual is (e.g., sex and season) were not significant  within this study.  

In addition to testing the bold and aggressive behavior of G. falcatus, I also analyzed  their territorial contests to determine the outcomes between size-matched individuals and what  characteristics might drive these results. I conducted 86 size-matched contests that included three  categories: intrasexual females, intrasexual males, and intersexual. The same individual won the  majority (84%) of repeated trials but questions regarding what is driving these results, individual  recognition or behavioral consistency, remain. Of the intrasexual contests (females and males),  residents won the majority of contests supporting previous work that has identified a bias  towards the resident in matched contests. On the other hand, during intersexual contests there was a substantial decrease in the proportion of contests won by residents. Further analysis  determined that males were winning more frequently than females in intersexual contests. While  it remains unknown why this shift has occurred, I hypothesize that sexual dimorphism in the  weaponry of G. falcatus is impacting the resource holding power and the perceived strength of  their competitor.  Overall, this thesis provides a behavioral characterization of G. falcatus and how their  behavior may influence their success as invasive species, although additional studies should be  performed to gain a deeper understanding of this invasion. This study also uncovered an  interesting trend in the contest outcome during intersexual contests, which have rarely been  included in previous work and proposes a hypothesis to explain what might be driving  differences in context outcomes between females and males. Finally, this thesis has identified an  overall lack of studies focused on the role of behavior in the invasions of marine crustaceans and  how it may differ from other taxa (e.g., terrestrial vertebrates).

Friday at 1:00 pm Limahuli Garden and Preserve on Kaua‘i

Zoom Link
Meeting ID: 861 9484 9463
Passcode: bryophyte

“Shedding a light on bryophyte distribution and facilitation: exploring light, microhabitats, and invertebrate associations.”
Date: 04/18
Speaker: Kassandra Jensen
Botany Graduate Program MS student

Bryophytes (mosses, liverworts, and hornworts) are underrepresented in conservation and restoration efforts, yet they play critical roles in maintaining ecosystem health. Globally, bryophytes have been shown to facilitate seed germination and seedling growth, as well as increase resources for invertebrates which may then pollinate plants or become food for other animals. This study is one part of a larger collaborative research project in Limahuli Stream in Hāʻena, Haleleʻa, Kauaʻi, which aims to understand the ecological foundations of Indigenous resource management. As one component of this work, we explored the influence of canopy openness and examined how variation in daily mean light intensity affects bryophyte abundance and diversity in the stream. We documented bryophyte identity and cover in four sites, using 8-22 transects per site and a total of 671 0.25×0.25 cm plots within the transects in order to capture the variation in bryophyte habitats. The effect of daily mean light intensity on abundance varied across habitat types. In wet habitats (e.g. waterfalls), bryophyte abundance had a nonlinear relationship with increasing mean daily light intensity, increasing from shady to intermediate light intensity, then decreasing from intermediate to high light intensity. The inverse relationship was seen in dry (e.g. dry rocks) and intermediate habitats (e.g. substrates at the water’s edge), where bryophyte abundance declined from low to intermediate light intensity, then increased from intermediate to high light intensity. Bryophytes forming dense, upright mats (called turfs) were positively associated with mean daily light intensity. The effect of bryophyte abundance on the probability of invertebrate presence also varied across habitat type and was significant in pools, rock edges, rock overhangs, and dry rocks. Additionally, mat-forming bryophytes were positively associated with invertebrate presence. These findings can guide restoration efforts, including outplanting decisions, canopy management, and reintroduction of bryophyte species to streams. As Hawai‘i faces threats from climate change and habitat loss, these insights are critical for addressing the urgent need to conserve biodiversity and restore degraded ecosystems.