Mercury Accumulation in the Water Column, Stream Sediments and Larval Black Fly (Diptera: Simuliidae) Tissue in Coastal Streams of Alabama, USA Chelsea E. Daniel & John W. McCreadie Received: 8 October 2013 /Accepted: 12 February 2014 /Published online: 2 March 2014 # Springer International Publishing Switzerland 2014 Abstract Larval black flies (Diptera: Simuliidae), which inhabit streams and rivers, are both filter-feeders and a dominant part of the macroinvertebrate commu- nity. As filter-feeders, these insects are potentially an important entrance point for mercury into lotic food webs. The objectives of our study were to (1) document mercury concentrations in the water column, streambed sediments, and larval black fly tissue in select streams in coastal Alabama, USA, over both spatial (among streams) and temporal (across and within season) gradi- ents and (2) determine if levels of mercury in stream ecosystems can be predicted based on stream predictors. Mercury was found consistently in both the black fly larval tissues and streambed sediments but was not detected in the water column. The range of total mercury found in larval tissue and stream sediments varied be- tween 23.73–142.05 and 0.60–56.98 ppb, respectively. Mean mercury levels in both tissue and sediments show significant variation among summer, fall, and spring collections. In addition, mercury levels in tissue and sediments were significantly associated with dissolved oxygen, conductivity, or temperature within a season. Keywords Mercury . Black flies . Simuliidae . Stream sediment . Seasonal variation 1 Introduction High concentrations of mercury in fish, even in remote areas, are concerning due to the potential effects on human health related to consumption of fish (AMAP 1998; Wright and Welburn 2002). Mercury can enter streams through a variety of pathways, with a number of toxic consequences to the biota (Lindqvist 1985; French et al. 1999; Fitzgerald et al. 1998; Boening 2000; George and Batzer 2008). Of particular interest is the entry of mercury into lotic (= stream) food webs, though little is known about how this is accomplished in lower trophic levels (Mason et al. 2000). One point of entry into the lotic food web at lower levels, however, is through the actions of filter-feeding organisms. Larval black flies (Diptera: Simuliidae), which inhabit streams and rivers, are filter-feeders (Currie and Craig 1988) and a dominant part of the macroinvertebrate community (Adler and McCreadie 1997; Adler et al. 2004). Adults, in contrast, are terrestrial, with females typically requiring a blood meal to develop eggs and both sexes requiring nectar for energy (Adler et al. 2004). Accordingly, these insects have strong links to both aquatic and terrestrial ecosystems. As filter-feeders, lar- val black flies are potentially an important entrance point for mercury into lotic food webs (Harding et al. 2006). Larval black flies can occur in very high densities and serve as prey to a variety of invertebrate and vertebrate predators (Crosskey 1990; Adler et al. 2004) and there- fore likely to be a significant source for mercury bioac- cumulation in stream food webs. Furthermore, they may Water Air Soil Pollut (2014) 225:1907 DOI 10.1007/s11270-014-1907-z C. E. Daniel : J. W. McCreadie (*) Biology, University of South Alabama, Mobile, AL 36688, USA e-mail: jmccread@southalabama.edu C. E. Daniel e-mail: cedaniel10@gmail.com