We investigated the impact of intertidal groundwater seepage on benthic microalgae and macrofauna in 4 study sites located in 2 large tidal flat ecosystems along the western coast of Korea by comparing the chemical, physical, and biological characteristics of 'glossy' seepage sites with those of nearby areas without visually distinct groundwater discharge (dry sediment surface). At 3 of the 4 sites, sediment properties as well as pore water chemistry were similar in groundwater seepage and dry areas. At the 4th study site, the groundwater seepage areas were more coarsegrained compared to the dry areas. Here, the groundwater seepage also had lower salinity and higher nutrient concentrations than the pore water of the dry area and the seawater in a nearby tide pool. Although diatoms were the dominant algal class in seepage and dry areas alike, the seepage areas in 3 of the sites had elevated contributions of other marker pigments such as chlorophyll (chl) b compared to the dry areas. Chl a concentrations were higher in all seepage areas compared to dry areas, and all dry areas had high pheophytin a:chl a ratios, indicating a substantial amount of degraded algal material. In the seepage areas of 3 of the sites, we found large numbers of the snail Batillaria cumingi, while crab burrows of Scopimera sp. were only present in the neighboring dry areas. Correlations of sediment chl a concentrations with physicochemical properties of the ambient pore water indicated that microphytobenthos responded specifically to groundwater seepage, which may provide shelter from desiccation and salt stress during emersion of the tidal flat. Our results suggest that globally common groundwater seepage significantly impacts the ecosystem structures and microphytobenthos production of the tidal flats.KEY WORDS: Groundwater · Seepage · Microphytobenthos · Macrofauna · Intertidal · Pigments · Tidal flat
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 407: [159][160][161][162][163][164][165][166][167][168][169][170][171][172] 2010 Intertidal microphytobenthos, i.e. the assemblage of bottom-living microalgae such as diatoms, is an important contributor to the benthic food chain (MacIntyre et al. 1996, Kang et al. 2003. Through resuspension, microphytobenthos can be transferred to pelagic systems as well (De Jonge & van Beusekom 1992). Furthermore, microphytobenthos can regulate diffusive nutrient fluxes between sediment and the overlying water column (Sundbäck et al. 1991). The relationship between microphytobenthos and ambient nutrient concentrations is often unclear. Generally, benthic microalgae, particularly from muddy sediments, are not nutrient limited (Underwood & Kromkamp 1999), and nutrient enrichment via the water column does not seem to have any effect on microphytobenthos biomass (Hillebrand & Kahlert 2002). On the other hand, microphytobenthos cultures can be maintained well with natural porewater (Admiraal et al. 1982), and microphytobenthos mats in the sandy sediment...