Constraints upon the response of fish and crayfish to environmental flow releases in a regulated headwater stream network

In dry climate zones, headwater streams are often regulated for water extraction causing intermittency in perennial streams and prolonged drying in intermittent streams. Regulation thereby reduces aquatic habitat downstream of weirs that also form barriers to migration by stream fauna. Environmental flow releases may restore streamflow in rivers, but are rarely applied to headwaters. We sampled fish and crayfish in four regulated headwater streams before and after the release of summer-autumn environmental flows, and in four nearby unregulated streams, to determine whether their abundances increased in response to flow releases. Historical data of fish and crayfish occurrence spanning a 30 year period was compared with contemporary data (electrofishing surveys, Victoria Range, Australia; summer 2008 to summer 2010) to assess the longer-term effects of regulation and drought. Although fish were recorded in regulated streams before 1996, they were not recorded in the present study upstream or downstream of weirs despite recent flow releases. Crayfish (Geocharax sp. nov. 1) remained in the regulated streams throughout the study, but did not become more abundant in response to flow releases. In contrast, native fish (Gadopsis marmoratus, Galaxias oliros, Galaxias maculatus) and crayfish remained present in unregulated streams, despite prolonged drought conditions during 2006-2010, and the assemblages of each of these streams remained essentially unchanged over the 30 year period. Flow release volumes may have been too small or have operated for an insufficient time to allow fish to recolonise regulated streams. Barriers to dispersal may also be preventing recolonisation. Indefinite continuation of annual flow releases, that prevent the unnatural cessation of flow caused by weirs, may eventually facilitate upstream movement of fish and crayfish in regulated channels; but other human-made dispersal barriers downstream need to be identified and ameliorated, to allow native fish to fulfil their life cycles in these headwater streams

The genomic landscape of balanced cytogenetic abnormalities associated with human congenital anomalies

Despite the clinical significance of balanced chromosomal abnormalities (BCAs), their characterization has largely been restricted to cytogenetic resolution. We explored the landscape of BCAs at nucleotide resolution in 273 subjects with a spectrum of congenital anomalies. Whole-genome sequencing revised 93% of karyotypes and demonstrated complexity that was cryptic to karyotyping in 21% of BCAs, highlighting the limitations of conventional cytogenetic approaches. At least 33.9% of BCAs resulted in gene disruption that likely contributed to the developmental phenotype, 5.2% were associated with pathogenic genomic imbalances, and 7.3% disrupted topologically associated domains (TADs) encompassing known syndromic loci. Remarkably, BCA breakpoints in eight subjects altered a single TAD encompassing MEF2C, a known driver of 5q14.3 microdeletion syndrome, resulting in decreased MEF2C expression. We propose that sequence-level resolution dramatically improves prediction of clinical outcomes for balanced rearrangements and provides insight into new pathogenic mechanisms, such as altered regulation due to changes in chromosome topology

Impacts of extreme events on southeastern Australian freshwater crayfish

Extreme events like wildfire, flooding and drought, and activities related to managing these events (fire dam, bridge and road construction and water regulation) potentially impact freshwater crayfish populations, although limited information exists. Our study analysed abundance data for four freshwater crayfish species across an 11-year period, including pre- and post-wildfire and post-flooding data, and described the impacts of human actions on their populations in the Grampians National Park in Victoria, Australia. Wildfire and flooding were generally associated with reduced crayfish abundances for Euastacus bispinosus, Cherax destructor, Geocharax falcata and Gramastacus insolitus, but in some habitats, C. destructor, G. falcata and G. insolitus did not decline. A general trend of decreasing abundances for all species was evident over the study period, likely due to the landscape-scale impacts of wildfire, flooding and the shrinking of available habitat during drought. Southeastern Australia is a crayfish biodiversity hot-spot and increased frequencies of wildfire, flooding and drought are forecast for this region as climate change progresses, threatening crayfish populations. Therefore, it is important that disaster recovery management seeks to minimise additional damage to crayfish habitat availability and connectivity

Seasonal variability in whale encounters in the Western Antarctic Peninsula

Cetacean sighting surveys were conducted as part of nine multidisciplinary research cruises over late summer, autumn and winter of 2 years (2001&ndash;2003) during the Southern Ocean Global Ocean Ecosystems (SO GLOBEC) program. Sea-ice cover differed markedly between years, with apparent effects on cetacean distribution. No ice was present until late June in 2001, while the previous winter sea ice never fully retreated (&gt;30% cover) during the 2002 or 2003 summer, thus increasing the proportion of thicker and more complex ice, including multi-year floes. Humpback (237 sightings; 537 individuals) and minke (103 sightings: 267 individuals) whales were the most commonly detected species. Data from seven comparable cruises were used to identify habitat for minke and humpback whales over five geographically distinct spatial divisions in the study area. In all years, both species were predominantly found in near coastal habitat, particularly in the fjords where complex habitat likely concentrated prey. In 2002 and 2003 the presence of sea ice provided additional feeding habitat, and the numbers of minkes (in winter) and humpbacks (late summer and autumn) in the area doubled compared with 2001. Humpbacks in particular were concentrated at the ice boundaries during late summer and autumn, while minke numbers increased in the winter that followed and occupied ice-covered areas along the entire shelf edge. Important resource sites for these species are mainly located in near-coastal areas and are used in all years, but when ice margins exist and intersect with resource sites they attract much larger numbers of animals due to the dynamics between sea ice and prey.<br /

Numbers of adult and juvenile fish and crayfish recorded for each stream in summer, per 100

<p>Adult and juvenile fish sizes (<i>G. oliros</i> based on <i>G. olidus</i>) from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091925#pone.0091925-Howson1" target="_blank">[20]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091925#pone.0091925-Harris1" target="_blank">[30]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091925#pone.0091925-Barbee1" target="_blank">[51]</a>. Adult and juvenile crayfish sizes (OCL) for <i>Geocharax falcata</i> were used from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091925#pone.0091925-Johnston2" target="_blank">[52]</a>. P =  present, not measured (too few or seen and not caught).</p

Diagram of the study streams (named in bold) in the Victoria Range, showing flow regimes and representing conditions at peak dryness, without summer passing flows (solid lines = perennial flow, dashed lines = seasonal flow with perennial pools and dotted lines = seasonal, completely dry) and weirs (‘U’ shapes).

<p>Survey sites denoted by ‘<b>x</b>’: primary sites were upstream and downstream of weirs, and at similar elevations on unregulated streams; all potential fish/crayfish refuges were sampled. Sites with faint ‘x’ were in surveys prior to this study, and were visited in summer 2008; they were subsequently dropped as they were not needed to characterize the unregulated streams for comparison with the regulated ones. General flow direction is from right to left. Note that this is a schematic diagram and is not to scale.</p

<i>Geocharax</i> sp. nov. 1 abundance for each stream per 100 m sampling effort.

<p><i>Geocharax</i> sp. nov. 1 abundance for each stream per 100 m sampling effort.</p

Presence of fish and crayfish in the eight streams at each sampling time, compared with historical presences.

<p>Compiled from Raadik (1996) and Jackson and Davies (1983) as well as author's unpublished data from 2006–2007. Bold indicates species found upstream of weirs; underlined indicates rare or encountered infrequently (i.e. very patchily distributed, in one place in channel: not given for historical occurrences); ^# denotes almost all animals caught electrofishing the unregulated streams in 2007 were these species.</p