Geology topics

Sarah Nash

Publications and source records attributed to Sarah Nash.

3 recordsLinked to original sources

USGS2024

Plant-derived products selectively suppress growth of the harmful alga Prymnesium parvum

Prymnesium parvum is a harmful alga found in brackish waters worldwide whose toxins can be lethal to aquatic organisms. Established field methods to control blooms of this species, however, are unavailable. Earlier studies showed that various extracts of giant reed ( Arundo donax ) can suppress P. parvum growth and that ellipticine, an allelochemical present in giant reed, is a potent algicide against this species. The unintended effects of giant reed products on nontarget organisms, however, are not fully understood. This study determined the effects of giant reed leachate (aqueous extract of dried chips) and ellipticine on growth of P. parvum and the green microalga Chlorella sorokiniana ; survival and reproduction of the planktonic crustacean Daphnia pulex ; and hatching success, larval survival, and larval swimming behavior of the teleost fish Danio rerio . Leachate made with 3 g chips L −1 was lethally toxic to P. parvum and D. pulex , stimulated C. sorokiniana growth, and impaired D. rerio behavior. Leachate at 1 g L −1 fully suppressed P. parvum growth, had moderate effects on D. pulex reproductive output, and had no effects on D. rerio . Ellipticine at 0.01 mg L −1 irreversibly inhibited P. parvum growth, acutely but reversibly inhibited C. sorokiniana growth, slightly delayed D. pulex reproduction, and had no effects on D. rerio . These observations suggest that when applied at appropriate concentrations, natural products derived from giant reed can be used as tools to specifically control P. parvum growth with minimal effects on nontarget species.

Water↗

USGS2024

Factors affecting the density of Metabetaeus lohena (Decapoda: Alpheidae) at a high-density anchialine pool environment on the Kona Coast of the Island of Hawai‘i

Caridean shrimps (Caridea) are the dominant macroinvertebrates in most anchialine ecosystems. Hawaiian anchialine ecosystems, primarily composed of shallow surface pools connected to the ocean via hypogeal networks of cracks, tubes, and other voids, support 10 caridean shrimp species, including two federally listed as endangered. Little is known about most of these species. The objective of this study was to identify factors that affect the abundance and distribution of Metabetaeus lohena (Alpheidae), an uncommon species found across the Hawaiian Archipelago, at Kaloko-Honokōhau National Historical Park, Island of Hawai‘i. This park supports the highest concentration of anchialine pools in the State of Hawai‘i and is critical to protecting this threatened ecosystem. During 2017, we measured the density of M. lohena during nighttime surveys, as well as a variety of other biological, physical, and chemical parameters, in 130 pools. Metabetaeus lohena occupied 71.5% of the pools surveyed, with a mean density of 7.32 individuals/m 2 (95% CI = 5.14–9.49). Invasive fish and the endemic shrimp Halocaridina rubra (Atyidae) had the strongest effects on M. lohena density, with negative and positive relations, respectively. In the first estimate of M. lohena density at this scale, our data indicate that Kaloko-Honokōhau supports about 11,480 shrimp (95% CI = 8,054–14,906) in the pools surveyed. Furthermore, our models predict that this park could support an additional 1,695 individuals (95% CI = 955–3,008) for a population of about 13,175 shrimp if fish were removed from 19 pools in which M. lohena are absent.

Hawaii↗

USGS2022

Characterization of a small population of the orangeblack Hawaiian damselfly (Megalagrion xanthomelas) in anchialine pools at Kaloko-Honokōhau National Historical Park, Hawai‘i Island

The endangered orangeblack Hawaiian damselfly (Megalagrion xanthomelas) is a lowland inhabitant of freshwater and brackish wetland environments. Formerly one of the most widely distributed native insects in Hawai‘i, it now appears restricted to small populations on the islands of O‘ahu, Moloka‘i, Maui, and Hawai‘i. On Hawai‘i island, anchialine pools provide important habitat for M. xanthomelas, and Kaloko-Honokōhau National Historical Park (Park) supports one of only a few documented populations on the western side of the island. This study aimed to estimate the population size of M. xanthomelas at this Park, characterize its habitat, and identify substrates on which females oviposit eggs. We conducted visual surveys for adult M. xanthomelas at anchialine pools during June 2016–August 2017. On average, the observed population was 10.7 individuals per month (range = 5–20; standard error = 1.3). Males were observed 6.1 times more frequently than females, likely reflecting the less cryptic nature of males compared to females. Females exhibited oviposition behavior on a variety of substrates, but small branches were used most frequently. Factors restricting this population are poorly known, but invasive fish may limit its distribution across the Park. Removal of invasive fishes from anchialine pools and ‘Aimakapā Fishpond may restore much habitat for this rare species in the Park.

Hawai'i↗