Recovery of plankton from hurricane impacts in a large shallow lake

Abstract

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.

Ecological Responses of Lakes to Climate Change

“…An approach to gain insights into how such changes might affect lakes is to study the responses to contemporary events that are outside the range of typical conditions. For example, Zhu et al [23] examined the response of Lake Taihu in China to repeated hurricane strikes and discussed how storms of greater intensity or frequency of occurrence could lead to a loss of ecosystem resilience from these catastrophic events, and Ji et al [24] documented long-lasting changes in species composition of plankton in Lake Okeechobee (USA) after an unusual case of three major hurricanes impacting the lake in two successive years.…”

Physical and chemical impacts of a major storm on a temperate lake: a taste of things to come?

“…Extreme climatic events, such as storms, high winds, floods and heat waves, can have a major influence on aquatic ecosystems (Robson and Hamilton 2003 ; Jankowski et al 2006 ; Tsai et al 2008 ; Jöhnk et al 2008 ; Giling et al 2017 ; Kasprzak et al 2017 ; Ji et al 2018 ). There is evidence that the frequency and severity of extreme events are increasing as a result of directional climate change (Coumou and Rahmstorf 2012 ; Hansen et al 2012 ), and there is a growing realisation that predicting the effects of future climatic conditions on aquatic ecosystems must explicitly incorporate extreme events, superimposed upon the long-term climate trends.…”

Drivers of phytoplankton responses to summer storms in a stratified lake: a modelling study

“…Polymictic (i.e. mostly shallow) lakes are likely to react differently to storms, with more emphasis on sediment resuspension and uprooting of macrophytes (Ji et al 2018), and our model results are not applicable there. We assess scenarios covering a broad range of atmospheric and lake conditions, that reflect conditions present in many temperate, stratifying lakes.…”

“…Additionally, a deeper mixed layer can increase light limitation for growth (Diehl et al 2002) and deepening dilutes concentrations by mixing phytoplankton over a larger volume of water (Kuha et al 2016). Sediment resuspension due to shear stress in shallower parts of the lake may simultaneously release nutrients and limit light availability (Ji et al 2018). As such, there are conflicting effects of storms on nutrient and light availability (Stockwell et al 2020), and the net effect of a storm on phytoplankton concentrations may depend on lake physiography and lake state prior to the event.…”