The Deepwater Horizon (DWH) blowout and oil spill began on April 20, 2010 in the northern Gulf of Mexico (NGOM) deep sea (1525 m). Previous studies documented an impacted area of deep-sea floor totaling 321 km² and were based on taxonomy at the macrofauna family level and the meiofauna major taxonomic level. In the present study, finer taxonomic resolution of the meiofauna community was employed, specifically harpacticoid copepod family biodiversity. Severe or moderate impacts to harpacticoid family biodiversity were observed at 35 of 95 sampling stations, covering an estimated area of 2864 km², 8.9 times greater impacted area than previously reported. Sensitive and tolerant harpacticoid families were observed in the impact zone. The present study greatly expands the understanding of DWH deep-sea impacts in 2010 and demonstrates that the harpacticoid family-level response is the most sensitive indicator (reported to date) of this oil spill pollution event.

During May and June 2000, for the first time, benthic samples were collected from 43 stations in the northern Gulf of Mexico deep sea that included seven transects along the northern continental slope and abyssal plain ranging in depth from 625 to 3159m. A total of 54 tardigrades (36 identified) were extracted from samples, ranging in depth from 625 to 3150m. Collected tardigrades belong to five genera and represented eight species, Angursa bicuspis abyssalis (two specimens from 1401 and 2020m depth), four species of Coronarctus (29 specimens from 625 to 3159m depth), Euclavarctus convergens (one specimen from 2743m depth), E. thieli (one specimen from 2635m depth), Proclavarctus sp. (one specimen from 2600m depth), Styraconyx sp. (two specimens from 1565 and 2600m depth). The most abundant genus was Coronarctus (80.5% of identified species) and was present in most areas sampled with the exception of the central and Mississippi trough regions and comprised four species, Coronarctus laubieri (15 specimens), C. stylisetus (one specimen), C. disparilis (three specimens) and a new species C. mexicus (10 specimens). Tardigrades were mostly found in the western regions (NW, W, WC) and in deep waters, 2290m average depth. Analyses of tardigrade and depth collected gave a slight positive correlation (R2=0.029), while analyses of tardigrade and degrees longitude resulted in a slight negative correlation (R2=0.022). © 2011 Blackwell Verlag GmbH

Benthic harpacticoids were collected for the first time at Lake Tahoe, California-Nevada, United States. Two species were identified as members of the genus Attheyella Brady, 1880. The genus Attheyella comprises about 150 species within six subgenera, but only twelve species have previously been reported from North American freshwater habitats. The two new species of Attheyella described here have a 3-segmented endopod on P1 and 2-segmented P2–P4 endopods, the distal segment of exopod of P2–P4 has three outer spines, and the P5 has five setae on the exopod and six setae on the baseoendopod. Attheyella (Attheyella) tahoensis sp. n. most closely resembles A. (A.) idahoensis (Marsh, 1903) from Idaho, Montana, and Alaska (United States) and A. (A.) namkungi Kim, Soh & Lee, 2005 from Gosu Cave in South Korea. They differ mainly by the number of setae on the distal endopodal segment of P2–P4. In addition, intraspecific variation has been observed on the caudal rami. Attheyella (Neomrazekiella) tessiae sp. n. is characterized by the extension of P5 baseoendopod, 2-segmented endopod of female P2–P3, and naked third seta of male P5 exopod. The two new species are likely endemic to Lake Tahoe, an isolated alpine lake within the Great Basin watershed in the western United States.

A new genus and new species of the family Cletopsyllidae Huys & Willems, 1989 from deep-sea sediment in the Gulf of Mexico, are reported and fully described and illustrated. The new genus Pentacletopsyllus (type species: P. montagni sp. n.) can be distinguished from the four known genera of the family by antennule segmentation, length ratio of first and second endopodal segments of P1, and armature pattern on P5 exopod. It also differs from its sister genera by the rostrum being bifid at the tip, third segment of the female antennulea smooth posterior margin, the baseoendopod of P5 with biarticulate outer setophore bearing basal seta, and female caudal rami without lobate expansion. A revised key to species of the family Cletopsyllidae Huys & Willems, 1989 is provided.

Coastal waters are sensitive habitats that support high biodiversity and provide essential ecosystem goods. Changes in sedimentation regimes due to land-use and engineering activities in the coastal zone affect biodiversity and these habitats’ ecological value. This study aims to characterize the meiobenthic communities inhabiting the Zwin tidal lagoon, located on the border between Belgium and the Netherlands, and to evaluate to what extent the sedimentological characteristics and the quantity and composition of organic matter influence the composition and distribution of meiofauna. The meiobenthic community showed traits of a well-established population dominated by nematodes, followed by copepods + nauplii. Notably, meiofauna rapidly colonized the area after its opening to the sea in February 2019 (two years before sampling), showing that even very weak tidal currents were sufficient to suspend and transport these animals to the new environment. Our results suggest that the Zwin lagoon is a productive system with high food quality (i.e., PRT/CHO ≥ 1), predominantly of marine origin. Major structural differences in communities were related to the sedimentary environments at the investigated stations and estimations of the quantity of food. The present findings confirm that sedimentary dynamics and depositional processes, through their influence on sediment properties (e.g., grain size) and organic matter’s quantity and composition, shape meiofaunal communities and their vertical and horizontal distributions.