Thursday, May 21, 2015
13:30 - 15:00

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13:30 - 13:45: / 102DE THE CHRONOLOGIC RECORD OF BURROWING MAYFLIES (HEXAGENIA SPP.) IN SAGINAW BAY, LAKE HURON

5/21/2015  |   13:30 - 13:45   |  102DE

THE CHRONOLOGIC RECORD OF BURROWING MAYFLIES (HEXAGENIA spp.) IN SAGINAW BAY, LAKE HURON Return of burrowing mayflies has been identified as a management goal in lake rehabilitation plans in the Great Lakes since the 1980s. However, we do not know where mayflies were endemic and therefore, whether their use as a management goal is logical in specific areas. We constructed a chronologic record (1770-2001) of mayflies from mayfly tusks in sediments and historic records to determine that mayflies: were low in abundance between 1770 and 1800, indicating nymphs were endemic in the bay; increased and remained abundant between 1815 and 1959, in response to increased nutrients from watershed development; and, abundance declines 1959, as a result of nymph extirpation caused by eutrophication and resulting anoxia. Between 1991 and 2008, limited sampling and visual observations indicate mayflies had not yet begun to recolonize Saginaw Bay.

Don W Schloesser (POC,Primary Presenter), U.S. Geological Survey, Great Lakes Science Center, dschloesser@usgs.gov;


13:45 - 14:00: / 102DE TRENDS IN THE DISTRIBUTION AND ABUNDANCE OF HEXAGENIA SPP. IN SAGINAW BAY, LAKE HURON, 1954-2012: MOVING TOWARDS RECOVERY?

5/21/2015  |   13:45 - 14:00   |  102DE

TRENDS IN THE DISTRIBUTION AND ABUNDANCE OF HEXAGENIA SPP. IN SAGINAW BAY, LAKE HURON, 1954-2012: MOVING TOWARDS RECOVERY? Multiple anthropogenic disturbances to the Great Lakes have been linked to extirpation of the environmentally sensitive burrowing mayfly genus, Hexagenia, from Saginaw Bay, Lake Huron c1960. Following recent reports of proximate adult swarms, we surveyed Saginaw Bay to assess its nymphal Hexagenia population - an indicator of benthic health. We corroborated adult presence at three Tawas City, Michigan area locations in 2010 at densities of >17 adults/m2. Further, we found 1.5 nymphs/m2 from Ponar grab samples collected at 57 bay sites between 2009 and 2012 with nymphal presence at 15.8% of those sites. Additionally, we related sampling site abiotic conditions to nymphal presence using Zero-Inflated Poisson regression; model results indicate the probability of nymphal absence is positively correlated with sediment sandiness. Comparing current to prior bay sediment composition revealed that >75% of bay sediment contained >50% sand in 2012, up from about half of bay sediment c1975. While documentation of nearby adults and in-bay nymphs may indicate Hexagenia are recovering in Saginaw Bay, modeling results suggest that the observed increases in sediment sandiness may limit potential Hexagenia recovery.

Heather Siersma (Primary Presenter/Author), Wayne State University, heather.siersma@wayne.edu;


14:00 - 14:15: / 102DE BENTHIC HABITAT CONDITIONS AND THE POTENTIAL FOR RE-COLONIZATION BY HEXAGENIA MAYFLIES IN GREEN BAY, LAKE MICHIGAN

5/21/2015  |   14:00 - 14:15   |  102DE

BENTHIC HABITAT CONDITIONS AND THE POTENTIAL FOR RE-COLONIZATION BY HEXAGENIA MAYFLIES IN GREEN BAY, LAKE MICHIGAN The lower Green Bay, Lake Michigan ecosystem is expected to be in a state of recovery from past degradation; however, mayflies of the genus Hexagenia, a well-known bioindicator of water quality, were extirpated in the 1950s and have yet to make a return. Several experiments are in progress, including raising Hexagenia nymphs collected from the Mississippi River in aquaria containing sediment collected from Green Bay, and incubating Hexagenia eggs in field enclosures. This study seeks, based on experimental results gathered, as well as analysis of sediment composition, macroinvertebrate community metrics, and dissolved oxygen concentrations across the bay, to determine Hexagenia's potential for re-introduction and re-colonization. These large insects serve important ecological roles associated with bioturbation and providing a high-quality food base for foraging fish. Their renewed presence in Green Bay would likely prove beneficial for higher trophic levels and the enhancement of fisheries, as well as an important indication of the bay's improving habitat quality.

Christopher Groff (Primary Presenter/Author), University of Wisconsin-Milwaukee School of Freshwater Sciences, cmgroff@uwm.edu;


Jerry Kaster (Co-Presenter/Co-Author), University of Wisconsin-Milwaukee School of Freshwater Sciences, jlk@uwm.edu;


14:15 - 14:30: / 102DE THE ROLE OF STRATIFICATION ON THE APPARENT TROPHIC POSITION OF COPEPODS IN LAKE MICHIGAN AS REVEALED BY THE NITROGEN STABLE ISOTOPE

5/21/2015  |   14:15 - 14:30   |  102DE

THE ROLE OF STRATIFICATION ON THE APPARENT TROPHIC POSITION OF COPEPODS IN LAKE MICHIGAN AS REVEALED BY THE NITROGEN STABLE ISOTOPE Due to the difficulty of sampling during winter months, information on full seasonal dynamics of zooplankton in the Great Lakes is limited. To examine seasonal trends in zooplankton feeding within Lake Michigan we monitored nitrogen stable isotope composition for three copepod species and seston between the months of January and September. Over the winter, the 15N:14N ratios for all three copepod species were high relative to seston, with values similar to those observed for lake trout in Lake Michigan. Following thermal stratification the 15N:14N ratios for all three species and seston dropped substantially. We suggest that this overall seasonal trend could be related to a switch in nitrogen source at the base of the food. The large hypolimnetic calanoid ,Limnocalanus macrurus, maintained a 15N:14N ratio higher than that of the other two copepod species measured. We hypothesize that differences between copepod species reflect difference in preferred feeding depths, which are distinguishable due to vertical differences in seston nitrogen isotope ratios within the water column.

Zac Driscoll (Primary Presenter/Author), UW-Milwaukee School of Freshwater Sciences, zgd@uwm.edu;


Harvey Bootsma (Co-Presenter/Co-Author), University of Wisconsin-Milwaukee, hbootsma@uwm.edu;


14:30 - 14:45: / 102DE IMPACTS OF THERMAL AND FLOW ALTERATION ON BENTHIC STREAM MACROINVERTEBRATES DOWNSTREAM OF WATER SUPPLY RESERVOIRS

5/21/2015  |   14:30 - 14:45   |  102DE

IMPACTS OF THERMAL AND FLOW ALTERATION ON BENTHIC STREAM MACROINVERTEBRATES DOWNSTREAM OF WATER SUPPLY RESERVOIRS The effects of temperature and flows on benthic macroinvertebrates have been documented; however, the combined effect of thermal and flow alteration caused by impoundments is less studied. We assessed the impact of thermal and hydrologic regimes on macroinvertebrates in 14 Massachusetts streams: six impounded by water supply reservoirs, two impounded by unmanaged reservoirs, and six unimpounded control streams. Transducers installed in 2012 and 2013 have continuously measured temperature and pressure every 15 minutes. We sampled benthic macroinvertebrates in riffle habitats in each stream in May 2014 and identified taxa to family or genus. Average abundances of tolerant taxa in the families Chironomidae and Simuliidae were higher in streams below water supply reservoirs than in control streams. In contrast, richness of sensitive EPT taxa was greater in control streams (16.7 ± 2.6) than downstream of water supply reservoirs (12.8 ± 2.9). Our results suggest that water supply reservoirs alter macroinvertebrate assemblages. Analyses examining linkages between thermal and hydrologic metrics and macroinvertebrates will be used to determine potential mechanisms of impairment and identify management approaches to minimize impoundment impacts to stream ecosystems.

Allyson Yarra (Primary Presenter/Author), University of Arkansas, ayarra@email.uark.edu;


Todd Richards (Co-Presenter/Co-Author), Massachusetts Division of Fisheries and Wildlife , todd.richards@state.ma.us;


Allison Roy (Co-Presenter/Co-Author), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;


14:45 - 15:00: / 102DE HABITAT USE BY DIFFERENT MITOCHONDRIAL LINEAGES OF THE ATYID SHRIMP PARATYA AUSTRALIENSIS IN STREAMS OF MELBOURNE, AUSTRALIA

5/21/2015  |   14:45 - 15:00   |  102DE

HABITAT USE BY DIFFERENT MITOCHONDRIAL LINEAGES OF THE ATYID SHRIMP PARATYA AUSTRALIENSIS IN STREAMS OF MELBOURNE, AUSTRALIA The atyid shrimp Paratya australiensis is a complex of closely related genetic lineages, of which 5 occur across Melbourne. Previous studies examining habitat use by P. australiensis have not considered variation between lineages. We examined habitat use and associations with conspecific lineages, for 3 demographic classes of 2 lineages of P. australiensis. We found strong associations with increasing levels of macrophyte cover for both lineages across demographic classes and both lineages were positively associated with conspecific lineages. Finding that both target lineages are strongly associated with increasing macrophyte cover indicates, regardless of genetic diversity, macrophyte cover is universally important to P. australiensis. The occurrence of different lineages in the same patches could indicate reproductive isolation between lineages or alternatively that secondary contact between them has occurred relatively recently. If foreign lineages of P. australiensis were introduced into a stream where another lineage occurs – and they were not reproductively isolated – they are likely to inhabit the same habitat patches, thereby increasing the potential of hybridisation and ultimately the extinction of the local lineage.

Anthony Lovell (Primary Presenter/Author), University of Melbourne, alovell@student.unimelb.edu.au;