A Review of Nontraditional Biomanipulation

Abstract

The aim of this review is to identify problems, find general patterns, and extract recommendations for successful management using nontraditional biomanipulation to improve water quality. There are many obstacles that prevent traditional biomanipulation from achieving expectations: expending largely to remove planktivorous fish, reduction of external and internal phosphorus, and macrophyte re-establishment. Grazing pressure from large zooplankton is decoupled in hypereutrophic waters where cyanobacterial blooms flourish. The original idea of biomanipulation (increased zooplankton grazing rate as a tool for controlling nuisance algae) is not the only means of controlling nuisance algae via biotic manipulations. Stocking phytoplanktivorous fish may be considered to be a nontraditional method; however, it can be an effective management tool to control nuisance algal blooms in tropical lakes that are highly productive and unmanageable to reduce nutrient concentrations to low levels.Although small enclosures increase spatial overlap between predators and prey, leading to overestimates of the impact of predation, microcosm and whole-lake experiments have revealed similar community responses to major factors that regulate lake communities, such as nutrients and planktivorous fish. Both enclosure experiments and large-scale observations revealed that the initial phytoplankton community composition greatly impacted the success of biomanipulation. Long-term observations in Lake Donghu and Lake Qiandaohu have documented that silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) (two filter-feeding planktivorous species commonly used in management) can suppress Microcystis blooms efficiently. The introduction of silver and bighead carp could be an effective management technique in eutrophic systems that lack macrozooplankton. We confirmed that nontraditional biomanipulation is only appropriate if the primary aim is to reduce nuisance blooms of large algal species, which cannot be controlled effectively by large herbivorous zooplankton. Alternatively, this type of biomanipulation did not work efficiently in less eutrophic systems where nanophytoplankton dominated.

Silver carp exhibited an enhanced ability of biomanipulation to control cyanobacteria bloom compared to bighead carp in hypereutrophic Lake Taihu mesocosms

“…Consequently, grazing pressure from zooplankton on phytoplankton, in terms of fish manipulation within seriously polluted lakes, could be neglected. Zhang et al (2008) proposed that if the lake is shallow and dominated by net phytoplankton, the removal of algae is usually efficient when non-classic manipulation is undertaken. Particles under 10 m, for instance, were found to be the minimum size that silver carp would collect (Smith, 1989).…”

“…We focus on two vital points that could determine the final success of algal control: (1) the filter feeder density that integrates the quantity of algal control with the risk of a fish's introduction and with the economic effects of the fish's growth; and (2) the fish culture mode which refines the planktonic species composition in static and dynamic situations. Zhang et al (2008) concluded that some field studies on scales from mesocosmic to full-lake have indicated that filter-feeding carps reared at 30-70 g m −3 could most effectively avoid the rapid growth of algae. The same result was predicted by a bifurcation model conducted by Attayde et al (2010), which showed that omnivores dry weight at 20 g m −3 (approximately 50 g m −3 wet weight) adjusts the plankton community at a stable rate.…”

Biomanipulation in mesocosms using silver carp in two Chinese lakes with distinct trophic states

“…Due to their high mass-specific nutrient excretion rate (Vanni, 2002), zooplankton is regarded as an important part of nutrient cycling in the water column. However, zooplanktons are frequently suppressed after the introduction of silver carp (Zhang et al, 2008;Xiao et al, 2010) in mesocosms such as the enclosures in the present study. The absence of large planktivorous zooplankton may reinforce the importance of fish in nutrient cycling.…”

“…Silver carp at moderate densities can effectively remove colonial Microcystis (Xie, 2003;Zhang et al, 2008), resulting in decreased chlorophyll-a. This pattern was observed in the Lake Taihu portion of our experiment but was reversed in the Lake Erhai enclosures.…”

“…The enhancement of silver carp in severely polluted lakes has been identified as a way to regulate water quality (Xie, 2003). The long-term stocking of silver carp in Lake Donghu and Lake Qiandaohu in China are successful cases (Zhang et al, 2008) where the manipulations of fisheries have alleviated water blooms. However, using silver carp to enhance environmental conditions has generally been confined to a relatively small scope and is most often used to treat lakes that suffer from heavy cyanobacteria Aquaculture 452 (2016) [233][234][235][236][237][238] blooms that cannot be controlled by zooplankton (Jeppesen et al, 2012).…”