Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific

Abstract

A key step in identifying global change impacts on species and ecosystems is to quantify effects of multiple stressors. To date, the science of global change has been dominated by regional field studies, experimental manipulation, meta-analyses, conceptual models, reviews, and studies focusing on a single stressor or species over broad spatial and temporal scales. Here, we provide one of the first studies for coastal systems examining multiple stressor effects across broad scales, focused on the nursery function of 20 estuaries spanning 1,600 km of coastline, 25 years of monitoring, and seven fish and invertebrate species along the northeast Pacific coast. We hypothesized those species most estuarine dependent and negatively impacted by human activities would have lower presence and abundances in estuaries with greater anthropogenic land cover, pollution, and water flow stress. We found significant negative relationships between juveniles of two of seven species (Chinook salmon and English sole) and estuarine stressors. Chinook salmon were less likely to occur and were less abundant in estuaries with greater pollution stress. They were also less abundant in estuaries with greater flow stress, although this relationship was marginally insignificant. English sole were less abundant in estuaries with greater land cover stress. Together, we provide new empirical evidence that effects of stressors on two fish species culminate in detectable trends along the northeast Pacific coast, elevating the need for protection from pollution, land cover, and flow stressors to their habitats. Lack of response among the other five species could be related to differing resistance to specific stressors, type and precision of the stressor metrics, and limitations in catch data across estuaries and habitats. Acquiring improved measurements of impacts to species will guide future management actions, and help predict how estuarine nursery functions can be optimized given anthropogenic stressors and climate change scenarios.

Are coastal habitats important nurseries? A meta‐analysis

“…We relied on the authors of the original publications to supply information on such variables, but unfortunately these were not consistently reported enough to support rigorous analysis (see Supporting Information). A recent meta‐analysis also suggested that abiotic conditions can greatly influence the nursery function of coastal habitats (Igulu et al., ), and other reviews of nurseries along the Northeast Pacific (Hughes et al., ) and Northeast Atlantic coasts (Brown et al., ) found that numerous human‐induced stressors can pose a risk to the nursery function (Toft et al., ). To date, however, explicit examples of nursery impairment due to anthropogenic or other environmental factors are rare and should be considered as an important next step for nursery research.…”

Multiple stressors and recruitment failure of long-lived endangered freshwater mussels with a complex life cycle

“…However, this highlights the importance of efforts to understand causal mechanisms for conservation biology (Hof et al, 2011). Studies on multiple stressors have mostly focussed on abundance or presence/absence data (e.g., Toft et al, 2018).…”

Changing estuaries and impacts on juvenile salmon: A systematic review

“…There is now a substantial body of work on the biological impacts of changing estuaries (e.g. Cloern et al, ; Toft, Cordell, Simenstad, & Stamatiou, ). To make informed decisions on the management of a variety of estuary types, from those that have been impacted for hundreds to thousands of years, to those that may be closer to ‘pristine’, there is a need to synthesize the body of knowledge.…”