Toxicity of Atrazine to Marine Invertebrates Under Flow-Through Conditions—Eastern Oyster (Crassostrea virginica) and Mysid Shrimp (Americamysis bahia)

The triazine herbicide atrazine is routinely detected in freshwaters, and has also been detected in coastal waters in Europe and the US. Relatively few atrazine studies have been conducted with estuarine/marine invertebrates. This study sought to contribute additional invertebrate atrazine toxicity data using model species, Eastern oyster (Crassostrea virginica) and Mysid shrimp (Americamysis bahia). Specifically, we investigated (1) acute effects on survival and growth of Eastern oyster, and (2) acute and chronic effects on survival, reproduction, and growth of the Mysid shrimp. No oyster mortality was observed following 96-h exposure to up to 17 mg a.i./L, but shell growth was reduced by 0.55% to 16% in 1.0, 9.2, and 17 mg a.i./L treatments, resulting in a 96-h EC50 of > 17 mg a.i./L. In the 96-h Mysid test, mortality rates of 5 to 70% were observed in 1.7, 2.4, 3.6, and 6.4 mg a.i./L treatments, and the 96-h LC50 was 5.4 mg a.i./L. Sub-lethal effects were observed among surviving Mysids exposed to ≥ 2.4 mg a.i./L. After 28 days of exposure to up to 1.1 mg a.i./L, there were no effects on survival or reproduction. The LOEC was 0.50 mg a.i./L, based on reduced body size, and the NOEC was 0.26 mg a.i./L. Overall, the results indicate that atrazine is slightly toxic towards Eastern oyster and moderately toxic to the Mysid shrimp under acute exposure conditions. These data will help to fill a gap in the literature and inform risk assessment of potential effects of atrazine towards estuarine/marine communities.

Discovery of Two New Astyanax Cavefish Localities Leads to Further Understanding of the Species Biogeography

The Astyanax species complex has two morphs: a blind, depigmented morph which inhabits caves in México and an eyed, pigmented surface-dwelling morph. The eyed morph can also be found in a few caves, sometimes hybridizing with the cave morph. This species complex has arguably become the most prominent model system among cave organisms for the study of evolutionary development and genomics. Before this study, 32 caves were known to be inhabited by the cave morph, 30 of them within the El Abra region. The purpose of this study was to conduct new surveys of the area and to assess some unconfirmed reports of caves presumably inhabited by troglomorphic fish. We describe two new localities, Sótano del Toro #2 and Sótano de La Calera. These two caves comprise a single hydrologic system together with the previously described cave of Sótano del Toro. The system is inhabited by a mixed population of troglomorphic, epigeomorphic, and presumably hybrid fish. Furthermore, Astyanax cavefish and the mysid shrimp Spelaeomysis quinterensis show a phylogeographic convergence that supports the notion that the central Sierra de El Abra is a biogeographical region that has influenced the evolutionary history of its aquatic community across species. The presumptive location of the boundaries of this biogeographical region are identified.

Two New Localities of Astyanax Cavefish Plus Revision of its Biogeography

The Astyanax species complex has two morphs: a blind, depigmented morph which inhabits caves in México and an eyed, pigmented surface-dwelling morph. The eyed morph can also be found in caves, sometimes hybridizing with the cave morph. This species complex has arguably become the most prominent model system among cave organisms for the study of evolutionary development and genomics. Before this study, 32 caves were known to be inhabited by the cave morph, 30 of them within the El Abra region. The purpose of this study was to conduct new surveys of the area and to assess some unconfirmed reports of caves presumably inhabited by troglomorphic fish. We describe two new localities, Sótano del Toro #2 and Sótano de La Calera. These two caves make a single hydric system together with the previously described cave of Sótano del Toro. The system is inhabited by a mixed population of troglomorphic, epigeomorphic and presumably hybrid fish. Furthermore, Astyanax cavefish and the mysid shrimp Spelaeomysis quinterensis show a phylogeographic convergence that supports the notion that the central Sierra de El Abra is a biogeographical region that has influenced the evolutionary history of its aquatic community across species. The presumptive location of its boundaries, which may limit cave-to-cave or surface-to-cave gene flow, are identified.

Characterizing the phytoplankton and zooplankton communities in Kootenay Lake: a time series analysis of 24 years of nutrient addition

Large-scale seasonal addition of limiting nutrients has been used for restoration in Kootenay Lake, British Columbia, since 1992 to mitigate cultural oligotrophication resulting from upstream hydropower development, river channelization, mysid shrimp introduction, and extensive tributary floodplain loss. Historical (1949) in-lake nutrient levels were targeted to stimulate bottom-up carbon transfer from native plankton communities to planktivorous and piscivorous fish populations that support popular fisheries. Analysis of 24 years of monitoring data assessed the effects of nutrient addition on the phytoplankton and zooplankton communities. Assessment involved comparisons of plankton community metric data from North Arm (1992–2003) and North + South arms (2004–2015) nutrient addition periods. A before–after, control–impact (BACI) analysis adjusted for these effects involved a series of phytoplankton and zooplankton metrics across the two lake arms. Time series analyses revealed significant serial correlation structure, significant increases in phytoplankton and zooplankton abundance and biomass, and increased stability within the phytoplankton and zooplankton communities. Results confirmed that adaptively managed nutrient restoration can effectively restore biological productivity and community structure in a large culturally oligotrophic lake.

Marine and estuarine leeches (Hirudinida : Ozobranchidae and Piscicolidae) of Australia and New Zealand with a key to the species

Marine leeches are sanguivorous parasites either on sea turtles (family Ozobranchidae) or on elasmobranch and teleost fishes (family Piscicolidae), with the exception of Mysidobdella, which may feed on mysid shrimp. The marine leeches of Australia and New Zealand are poorly known, especially those on teleost fishes. Collections of marine leeches from all major museums in Australia and New Zealand were examined, as well as many specimens sent to the author. Ozobranchus branchiatus and O. margoi were found on sea turtles in Australia. Seven genera and 14 species of fish leeches were found in Australia; 6 genera and 10 species of fish leeches were found in New Zealand. Two genera (Pontobdella and Branchellion) and four species (P. leucothela, P. moorei, B. australis and B. plicobranchus) occur in both Australia and New Zealand. No genus is endemic to Australia, but four species are endemic based on current records (Austrobdella bilobata, Austrobdella translucens, Trachelobdella leptocephali and Pterobdella platycephalus). Two genera (Bdellamaris and Leporinabdella) and three species (B. manteri, B. eptatreti, and L. digglesi) are endemic to New Zealand based on current records. The marine leeches of Australia and New Zealand are a mix of endemic species, those of tropical or subtropical origin, and those of subantarctic origin.