Mussel responses to flood pulse frequency: the importance of local habitat

Abstract

Summary 1. Understanding mechanisms behind the distribution of organisms along a gradient of hydrological connectivity is crucial for sustainable management of river–floodplain systems. We tested the hypothesis that frequency of flood pulses exerts a direct influence on the distribution of freshwater mussels (Unionoida) by creating a local environment that limits their fitness. 2. Multiscale habitat analyses combined with transplant‐rearing experiments were carried out with a focus on abundance, presence/absence, survival rates and growth rates of mussels. Sixty‐nine floodplain waterbodies (FWBs) were surveyed within a 15‐km lowland segment of the Kiso River in Japan. 3. The abundance of mussels significantly increased with increased frequency of inundation associated with flood pulses at the among‐FWB scale, while the probability of occurrence of mussels was negatively predicted by the amount of benthic organic matter at the within‐FWB scale. 4. Field‐rearing experiments showed that survival rates were low and growth rates nearly zero in infrequently inundated FWBs (these FWBs had no naturally occurring resident mussels). In such FWBs, hypoxia (DO < 2 mg L−1) was frequently observed near the bottom when temperature was optimal for mussel growth (>15 °C). 5. These findings demonstrated that flood pulse frequency was the most important factor in determining mussel distribution in FWBs because it directly limits mussels’ fitness by mediating local environmental factors, possibly dissolved oxygen (DO) levels. Successful restoration efforts for mussel habitat conservation should focus on processes that lead to improved local conditions.

Community structure and decadal changes in macrozoobenthic assemblages in Lake Poyang, the largest freshwater lake in China

“…Therefore, an improved understanding of macrozoobenthic assemblages is highly significant for developing efficient conservation and management strategies for floodplains. As is well-known, the distribution of benthic invertebrates in floodplain systems is influenced by abiotic habitat parameters such as water depth, current velocity, substratum stability, and grain size (Thomaz et al, 2007;Davidson et al, 2012;Negishi et al, 2012). Johnson et al (2004) showed that the variation of macrozoobenthic communities across sites in lakes is best explained by habitat-scale characteristics.…”

Terrestrialization alters organic matter dynamics and habitat quality for freshwater mussels (Unionoida) in floodplain backwaters

“…This study was conducted between 16 June 2008 and 19 August 2010 within a 15-km mid-segment of the Kiso River (see Negishi et al, 2012a for more details). The channel gradient was 0.15% with an average wetted main-channel width of c. 400 m during the base-flow period.…”

“…FPWs had a negligible abundance of macrophytes possibly due to hydraulic conditions unsuitable for their growth. frequency ranging from 0-to 0.85-year return periods; 0-year return period was applied to connected FPWs (see Negishi et al, 2012a for more details). Additionally, the main channel was also sampled at a near-shore (<20 m from the shore) sampling station (Table 1).…”

“…We conducted field sampling in 14 FPWs, nine for intensive investigation and five for additional sporadic investigation (Table 1). frequently flooded) (Negishi et al, 2012a;Fig. Among the 14 sites, five were connected, while nine were isolated.…”

“…Second, increased primary production from terrestrial or littoral vegetation within the floodplain could provide additional sources of coarse organic matter for FPWs (e.g. Negishi et al, 2012a). Flood pulse characteristics control composition and production of vascular plants within and around FPWs (Robertson, Bacon & Heagney, 2001;Van Geest et al, 2005).…”