Date: 12/15/2025 (Monday)
Time: 3:00 pm
Location: MSB 100 (In-person only)

Masters Thesis Defense:
“Integrated Assessment of Fecal Indicator Bacteria (FIB) and MIcrobial Source Tracking (MST) in American Samoa Watersheds”

Speaker: Nu Jahat Jabin
Microbiology MS Student

Abstract: American Samoa (AS) watersheds support various ecosystem services. The rapidly growing island population and its needs can compromise the water quality in the watersheds, posing a risk to public health and ecosystem integrity. Currently, AS relies on standard fecal indicator bacteria (FIB), namely enterococci and Escherichia coli, for monitoring stream and beach water quality, much like the US. This study assessed 50 soil and 41 water samples across five watersheds (classified from pristine to extensive) for FIB (enterococci, E. coli, Clostridium perfringens) and MST markers (human-associated CrAssphage and HF183, dog-associated BacCan-UCD, and pig-associated Pig-2-Bac). STV-based water quality standards for enterococci (130 MPN/100ml) and E. coli (410 MPN/100ml), utilized in AS, were not met by 80.5 and 65.9% of the stream samples, respectively. At least one of the four MST markers was detected in 36.4% and 44.4% of the water samples that did not comply with the enterococci or E. coli standards, respectively. At least one of the two human-associated markers were detected in 27.3% and 33.3% of the water samples that did not comply with the enterococci or E. coli standard, respectively, therefore indicating that the source of elevated levels of indicator bacteria in the majority of the cases was not sewage. Concentrations of the markers in the samples positive for markers did not correlate with any of the FIB tested (P>0.05 on all tests). Detection of human-associated markers was limited to two out of the five watersheds classified as extensive. Our limited validation of MST markers based on the 37 fecal samples of animals common in AS (farm pigs, dogs, fruit bats, chickens, birds) and six wastewater samples collected from two treatment plants indicated 100% sensitivity for all four markers. Human-associated marker (HF183) was detected in a single dog fecal sample (97.3% specificity), and dog-associated markers (BacCan-UCD) were detected in two chicken and pig samples (89.2% specificity); no cross-reactivity of CrAssphage and Pig-2-Bac were detected. All soil samples were negative for the human-associated markers, but dog-associated and pig-associated markers were detected in two and one soil sample, respectively. Both enterococci and E. coli were detected in 92.0% of soil samples, averaging 954 MPN/g and 1,375 MPN/g, respectively, likely implicating soils as the major source of elevated levels of FIB in AS watersheds.

Wednesday at 3:00 pm in Architecture 205

Zoom Link
Meeting ID: 340 861 7976
Passcode: limu

PhD Defense:
“Phylogeography, Dispersal, and Invasion Pathways
of Marine Rhodophyta in Hawai‘i and the Pacific”
Date: 04/16
Speaker: James Fumo
Marine Biology Graduate Program PhD student

Dispersal capacity of organisms in marine ecosystems explains population structure, biogeography, and phylogeography, and should be considered in ecosystem management. Understanding dispersal is particularly important for marine macroalgae, which are the foundation of marine ecosystems and provide numerous ecosystem services. Red algae, however, face numerous biological constraints limiting dispersal by propagules, which are negatively buoyant, non-flagellated, and attach rapidly to substrates. As such, dispersal to and within the remote Hawaiian archipelago may be difficult. Though long-distance dispersal by propagules is limited, it can be achieved by rafting on flotsam, which is increasingly abundant in the oceans. Hawai‘i’s marine algal biogeography, phylogeography, and dispersal capacities remain poorly understood, particularly in relation to dispersal barriers and the transport of nuisance taxa. Here I show through phylogeographic analyses that there are dispersal barriers for the red alga Amansia glomerata between the islands of Hawai‘i and Maui Nui (Maui, Moloka‘i, Lāna‘i), Maui Nui and O‘ahu, as well as between Kaua‘i and the remote and protected Papahānaumokuākea Marine National Monument (PMNM). These barriers largely match those found in similar studies on marine animals in the archipelago. Further, A. glomerata in Hawai‘i is split into four lineages which overlap in certain parts of their ranges and display a high level of molecular diversity. Assessments of population differentiation between islands yield relatively high values in comparison to animal groups. Comparisons between mesophotic and shallow collections revealed shared haplotypes. These shared haplotypes may provide support for ongoing connectivity between these environments with implications for mesophotic refugia and the habitat persistence of deep reefs. Additionally, through a modeling approach I show that dispersal of the putative non-native red alga Chondria tumulosa is likely aided by marine debris in PMNM. This is concerning as there is an abundance of large, floating, abandoned, lost, or discarded fishing gear in PMNM which acts as a habitat substitute in the open ocean. 

I also identify the oceanographic conditions and particle properties most likely to transport the species from Manawai, the first known location of the species, and show that rafting fragments are more likely to transit between atolls than tetraspores. This aligns with genetic assessments of population connectivity in C. tumulosa, which suggest high rates of asexual fragmentation. This result also helps guide early detection of the species on the atolls and islands to the southeast of Manawai. Finally, I use a backtracking connectivity model to show that the highest likelihood source locations for C. tumulosa are Japan’s Cape Inubo and Izu Islands, Johnston Atoll and the Line Islands, including Palmyra in the central Pacific, and the Galápagos Islands and Clipperton Atoll in the Eastern Tropical Pacific. While the macroalgal flora of PMNM is broadly composed of species that share affinities with Japanese and Indo-Polynesian regions, the model highlights specific source locations which should be targeted in the search for the species outside of the Hawaiian archipelago. I propose a framework for searching for C. tumulosa, beginning with eDNA surveys in model-guided source locations, followed by in-water surveys and DNA barcoding. This method utilizes a recently developed eDNA assay for C. tumulosa, minimizing costs and improving efficiency. An accompanying search for C. tumulosa in global herbaria is presented and identifies 12 species of Chondria which previously lacked genetic information and have distributions overlapping with the model-guided search regions. 

Collectively, this dissertation focuses on connectivity of macroalgal populations between the islands of the Hawaiian archipelago and beyond using both genetic and modeling approaches. This approach provides a more comprehensive understanding of the biogeography and phylogeography of macroalgae in Hawai‘i and the Pacific. Furthermore, it has broad utility and applicability for the inclusion of algae in inter-island connectivity indices and the assessment of the spread and origin of nuisance species.

Friday at 10:00 am in ARCH 205 

Zoom Link
Meeting ID: 271 915 3365
Passcode: limu
Thesis Defense:
“TESTING NOVEL TECHNIQUES TO MANAGE THE INVASIVE GREEN ALGA Avrainvillea erecta
(Berkeley) A.Gepp & E.S.Gepp IN COASTAL WATERS OF OʻAHU”
Date: 02/14
Speaker: Liv Wheeler,
Botany Graduate Program, Master of Science In Botany

Marine algal introductions threaten the biodiversity of Hawaiian reefs. With heavy
shipping traffic occurring on the south shore of Oʻahu, non-native plants are transported
to near shore habitats. Coastal urbanization has further degraded the native benthic
ecosystem. Psammophytic, or soft bottom habitats occur adjacent to Hawaiʻi fringing
reefs, starting at about 15-18 m depth, and remain poorly studied. These seagrass /
algal meadows adjacent to coral reefs occupying as much as 50 % of benthos in
Hawaiian shallow waters (<30m). This research focuses on the psammophytic plant
community. A newly introduced species of green alga, Avrainvillea erecta, has
established meadows on Oʻahu and spread to Maui, and Hawaiʻi Island communities.
The goal of this research was to monitor the growth and spread of A. erecta and
investigate management techniques to control its populations. Physical removal
treatments were applied over two years from 2020-2022, yet none of these removal
treatments significantly reduced the density of the plant within the study area. However,
initial abundance positively influenced the number of plants that did recover. Chemical
management, using 10 ml injections of 3% hydrogen peroxide, were tested in
mesocosm and in situ experiments. While the mesocosm experiment did not result in a
significant outcome, the outcome of in situ experiment were statistically significant,
using a linear regression model to show negative effects of hydrogen peroxide
treatment over time. Early detection and rapid response coordinated with hydrogen peroxide treatments appear to be critical actions managers might consider when
working to control this alga.
Link to Flyer

Friday at 12:00 pm on Zoom 

Zoom Link
Meeting ID: 821 9532 5004
Passcode: 120766
PhD Defense:
“Social and Ecological Dimensions of Forest Stewardship in Pacific Islands”
Date: 01/31
Speaker: Lauren Nerfa
Botany PhD Candidate

Forests face loss and degradation globally, yet they are essential for human and planetary health, hence their conservation and restoration are imperative. Tropical forests, particularly on islands, host high levels of biodiversity and endemism, and experience multiple threats due to climate change, invasive species, and other anthropogenic drivers of change. Major research gaps on tropical island forest conservation and restoration include establishing a better understanding of how human dimensions are incorporated into forest conservation efforts; the most effective methods to manage non-native species; and the impacts of climate change. In this thesis, I addressed these gaps by examining social and ecological aspects of forest conservation and restoration (together called stewardship) in two Pacific Island archipelagos: the Hawaiian Islands, and the Southern Line Islands. The main question being asked is: what are the drivers and limitations that promote or hinder the success of conservation and restoration? I used a combination of document analysis, interviews, vegetation surveys, and comparisons to historic studies to address: 1) What is the range of types of organizations focusing on terrestrial ecosystem stewardship in Hawaiʻi and how do these organizations incorporate human dimensions into their approaches and discourse? 2) What underlying values drive restoration practitioners and how do they define restoration success? 3) What restoration techniques affect metrics of restoration success in Hawaiian mesic forests? 4) How is vegetation of currently uninhabited islands affected by land-use history and an extreme El-Niño Southern Oscillation (ENSO) event, and what does this mean for restoration in the context of climate change? I found that organizations in Hawaiʻi incorporated the human dimensions in diverse ways, with no clear trends with respect to organization type; that all organizations involved local communities; and that the majority of organizations included cultural aspects in stewardship.Restoration practitioners in Oʻahu’s Waiʻanae mountains were motivated by a passion to protect and restore the unique and imperiled species and ecosystems of Hawaiʻi. I found that some of their measures of success were achieved, including native species predominance in the midstory of the restoration sites. Removing non-native trees by total cutting or girdle treatments led to better metrics of restoration success than the selective cutting of trees, but removal of non-native species alone was not sufficient to support native species regeneration in the understory. Furthermore, time since initiation of restoration, out-planting density, and weeding frequency did not affect indicators of restoration success over the timeframe of the restored forests that were studied (4-14 years post-initiation of restoration). In the Southern Line Islands, changes in species richness were noted on all islands since the historic studies, with a reduction in species richness found for most islands due to the disappearance of some non-native species which had been cultivated previously. There was some evidence of drought post-ENSO, with implications for the plant communities facing climate change.Takentogether, the findings provide a breadth of knowledge on social and ecological factorswhich can support effective terrestrial ecosystem stewardship in Pacific Islands and other similar tropical ecosystems.

Thursday at 1:00 pm in Bilger 152 

Zoom Link
Meeting ID: 823 1625 0756
Passcode: edna
M.S. Thesis Defense:
“Environmental DNA Reveals Hidden Coral Diversity in Hawai’i“
Date: 12/05
Speaker: Cécile Vimond
Zoology M.S. Candidate
SoLS, UH Mānoa

Knowledge of coral species diversity, community structure, and function has traditionally relied
on morphological variation to differentiate species. Yet, coral morphology and its relationship to
species boundaries are notoriously difficult to understand, leading to both under- and over-
estimates of diversity. However, better molecular data have transformed our understanding of
coral species boundaries. In agaricid corals, recent molecular studies have revealed numerous
cryptic taxa within single widespread nominal species in the Indo-Pacific. This high diversity of
morphologically cryptic taxa, combined with the ecologically cryptic nature of many agaricids,
provides an ideal opportunity to test an environmental DNA (eDNA) approach to assess
diversity in taxa that are both difficult to visually identify and sample. In the present study, the
mitochondrial cox1-1-rRNA intron was sequenced from water samples to evaluate agaricid
distribution and diversity across 32 sites on four Main Hawaiian Islands. A total of 9 distinct
clades of agaricids were detected, including several cryptic lineages within the nominal Pavona
varians. This eDNA approach identified more taxa than are known from visual surveys
conducted on shallow Hawaiian reefs. Significant differences in species richness and diversity
were observed across islands and sites. Analysis of the effect of environmental variation on
community composition identified three key factors shaping agaricid communities (rugosity,
sedimentation, and temperature). Overall, this study demonstrates the potential of eDNA to
uncover hidden coral diversity and elucidate patterns and of species diversity and community
composition among agaricids across the Hawaiian Islands.

Tuesday at 3:00 pm in St. John 011

Zoom Link
Meeting ID: 982 9721 2818
Passcode: orchid
Dissertation Defense:
“Phylogenetic and biogeographic origins of the Hawaiian endemic orchids Liparis hawaiensis, Anoectochilus sandvicensis and Peristylus holochila, and the identification and characterization of the root associated fungi of Liparis hawaiensis“
Date: 04/30
Speaker: Peter Wiggin
Botany PhD Candidate
SoLS, UH Mānoa

Orchidaceae is the most species rich plant family on earth, and orchids are noted for their myriad specializations. One such specialization is the minute seeds they produce which are adapted for wind dispersal. Despite this, there have been very few examples of long-distance dispersal by orchids. Although the Hawaiian Islands represent a diverse range of habitats and have been colonized by many different plant groups, the Orchidaceae is represented by only three native species. Moreover, although many lineages that colonized Hawaiʻi have exhibited fantastic radiations, the orchids of Hawaiʻi have not. This is particularly noteworthy given the remarkable diversification that the Orchidaceae is known for. My research utilized molecular phylogenetics to determine the biogeographic origins of the 3 endemic orchids of Hawaiʻi: Liparis hawaiensis, Anoectochilus sandvicensis, and Peristylus holochila. Results indicate that the most recent common ancestor of L. hawaiensis is from East Asia, and not North America as previously suggested. This study of Anoectochilus sandvicensis similarly demonstrated an East Asian origin, and is nested within a clade with species of Odontochilus and not with other species of Anoectochilus, and as such is now recognized as Odontochilus sandvicensis. Analyses of Peristylus holochila and its relatives indicate it is most closely allied with Platanthera species of northwestern North America, and is recognized now as Plantanthera holochila. Because orchids are obligated to form relationships with mycorrhizal fungi in order to germinate and complete their life cycle, this research also utilized a combination of sanger and next generation sequencing to investigate the fungal associations of Liparis hawaiensis. Plants from multiple populations on different islands harbor a diverse group of fungal endophytes in their roots and most notably form mycorrhizal relationships with a narrow range of Tulasnellaceae fungi. It is hoped that by disentangling some of the complex and long-standing biogeographic, evolutionary, and ecological questions regarding these endemic species, efforts to conserve them will be better equipped in the future.