Management of natural Ulva spp. blooms in San Quintin Bay, Baja California: Is it justified?

Abstract

According to Zertuche-González et al. (2009), Ulva spp. blooms, favored by oyster cultivation, are likely displacing subtidal meadows of Zostera marina in San Quintin Bay, Baja California. The authors propose a partial removal of the seaweed to reduce the risk of eutrophication and eelgrass displacement in the bay. We warn about the removal of Ulva spp. biomass by raising six arguments that emphasize the necessity of a historical and ecosystem-based management for San Quintin Bay. First, processes other than competitive exclusion by Ulva spp. blooms more likely explain changes of Z. marina subtidal meadows in the past decade. Second, there is no consistent evidence that oyster cultivation is promoting blooms of Ulva spp. and the loss of eelgrass. Third, the removal of Ulva spp. biomass is based on experiences of heavily anthropogenically eutrophic systems, while San Quintin Bay is not. Fourth, the proposed course of actions to restore eelgrass meadows ignores general historical baselines of estuarine and coastal systems by confusing what it means to be "pristine." Fifth, despite the important experimental evidence indicating strong top-down control in temperate seagrass meadows, Zertuche-González et al. (2009) underestimated the capacity of consumers in structuring dynamics of vegetated softbottom communities in San Quintin Bay. Sixth, Ulva expansa may exert positive effects on seagrass ecosystem properties and functions. Instead, we propose protection against the propagation of unsustainable practices in the bay, and the reintroduction of large consumers that are now absent in this ecosystem. An ecosystem-based analysis of the role of Ulva spp. on eelgrass dynamics is needed.

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“…sertularioides, This coincides with the characteristics of these highly adaptive, bloom-forming algal species (Cohen and Fong 2004;Thornber et al, 2008;Jorgensen et al, 2010;Teichberg et al, 2010). These may persist as dominant even in periodically or occasionally nutrient-poor environments, because of their capability of N storage (Naldi and Wheeler, 2002) and of organic nitrogen utilization in N-poor environments (Tyler and McGlathery, 2006).…”

Harmful algal blooms along the North American west coast region: History, trends, causes, and impacts

“…; Jousson et al, 2000;Walters et al, 2006), and Baja California (Ulva spp. ; Jorgensen et al, 2010;Zertuche-Gonzá lez et al, 2009) that have displaced native algal species and modified habitat, leading to losses in living resources and economic costs for eradication.…”

Upwelling‐influence, macroalgal blooms, and seagrass production; temporal trends from latitudinal and local scales in northeast Pacific estuaries

“…In some estuaries along the west coast of North America, new research suggests that large summer macroalgal blooms can be associated with nutrient-rich, ocean-derived water transported nearshore during periods of strong coastal upwelling (Brown and Ozretich 2009;Jorgensen et al 2010). Production of macroalgal blooms on the Oregon coast can be comparable to east coast systems.…”

“…Also in Oregon, mean summer biomass surpassed the threshold for negative effects on seagrass determined from research in Chesapeake Bay, U.S.A. (100 g dry wt m 22 ; Bricker et al 2003). However, ulvoid macroalgal effects on seagrass communities are understudied on the Pacific coast of North America (except see Nelson and Lee 2001;Kentula and DeWitt 2003;Jorgensen et al 2010) and it is unknown whether the classic paradigm seen in land-based eutrophic systems, with macroalgae having a negative effect on seagrass, holds across systems in this region where ocean upwelling is prevalent, but its strength is variable both latitudinally and seasonally.…”