Recovery of plankton from hurricane impacts in a large shallow lake

We quantified recovery of plankton in a large subtropical shallow lake from the catastrophic impacts of three successive major hurricanes. This assessment was possible because hurricanes passed directly over the lake amid an ongoing long‐term sampling programme that included nearly all components of the plankton, from bacteria to crustacean zooplankton. We compared attributes of plankton 5 years after the hurricanes to a pre‐hurricane period and to a period immediately after the storms. We evaluated both community‐level properties (biomass, biomass ratios, diversity, and dominance of major plankton groups) and species‐level properties (species absolute and relative biomass) at four sites in the lake representing different ecological zones. The hurricanes strongly affected water quality and plankton community structure. The lake experienced a regime shift, losing its submerged aquatic vegetation and becoming homogenous and turbid at all sampled sites. Five years after the storms, chemical and physical conditions recovered across the lake, with a few exceptions. Between 35 and 93 plankton species were lost at the sampling sites, with greatest losses in the phytoplankton. Relative species biomass displayed substantive changes too. Daphnia ambigua did not recover at three of the sites, Polyarthra vulgaris greatly increased lake‐wide, and at a central pelagic site, there was a total loss of heterotrophic nano‐flagellates and a much higher biomass of diatoms than before the hurricanes, despite recovery of irradiance, depth, nutrient levels and other attributes. Most community‐level properties were resilient, returning to pre‐hurricane conditions of total biomass, ratios of autotrophs to heterotrophs and ratios of protozoa to metazoa. This likely happened because of species compensation in the biodiverse community. The exception was at a central pelagic site, where the community‐level properties did not recover and nearly 50 per cent of species were lost. The community resilience, despite a regime shift, may have occurred because of a controlled lowering of water levels in the lake for flood protection, which led to regrowth of lost submerged aquatic vegetation (SAV) and migration of mud sediments back towards mid‐lake. In this lake and others with a history of high nutrient inputs, shallow depth and flocculent sediments, resilience may be low unless counter‐acting forces are able to push the system back after a regime shift.