Surprises surface from subsurface studies

Posted on March 26, 2010

Compared with the literature on the ecological impacts of flooding , there is little information on the responses of instream communities to droughts.  This is particularly true for the subsurface (hyporheic) fauna.  Recent studies have revealed that the hyporheic zone permits dynamic links between surface water and groundwater, provides ecosystem services such as nutrient storage, acts as a refuge for surface water species during drought, and supports a diverse fauna including a number of unique taxa.  English and Australian researchers have detailed the physical and ecological changes that occur as water levels drop during severe droughts.  In 2006, as the drought in theU.K.continued, the abundance and diversity of surface water invertebrates in the Little Stour River declined.  In contrast, the subsurface fauna showed a completely different response, with marked increases in abundance over the same period.  During droughts, it appears that surface and subsurface communities are affected by changes in temperature and other factors as well as by declining flow rates, and the results highlight the point that surface water is only one component of a larger interconnected hydrological system.  There’s room for a better understanding of linkages between surface and subsurface communities, and of lagged subsurface responses to  environmental variation.

Reference:  Stubbington, R., Wood, P.J. & Boulton, A.J.  2009.  Low flow controls on benthic and hyporheic macroinvertebrate assemblages during supra-seasonal drought.   Hydrological Processes 23, 2252–2263.