Invertebrates are declining in boreal aquatic habitat: The effect of brownification?

Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, Canada

“…Our findings align with those of Vilchis et al (2015) for piscivores and guilds without local breeding populations and, for the first time, highlight benthivores as the guild showing steepest 20-yr declines. Putative mechanisms behind these changes in abundance could include: redistribution in response to prey (demonstrated for Western Grebe; Wilson et al 2013), redistribution in response to predators (e.g., Middleton et al [2018] found that dive-feeding birds in the Salish Sea, including scoters, moved away from shore in response to the threat from Bald Eagle Haliaeetus leucogaster), factors operating in other parts of the ranges of longer distance migrants (e.g., climate-driven changes in aquatic invertebrate prey on boreal or arctic breeding grounds; e.g., Corcoran et al 2009, Arzel et al 2020, and changes to benthic and epibenthic food sources in the Salish Sea. Duck species that have benefited from ongoing conservation investment in > 80,000 km² of wetlands and adjacent Avian Conservation and Ecology 15(2): 20 http://www.ace-eco.org/vol15/iss2/art20/ lands in Canada, under the North American Waterfowl Management Plan (NABCI-Canada 2019), showed stable or increasing species-specific trends in the Salish Sea, including American Wigeon (Mareca americana), Northern Pintail (Anas acuta), and Green-winged Teal (Anas crecca).…”

Shifts in fine‐scale distribution and breeding success of boreal waterbirds along gradients in ice‐out timing and habitat structure

“…See Section 2.4 for further explanation [Colour figure can be viewed at wileyonlinelibrary.com] typically surrounded by forests and having poor emergent vegetation). Forest cutting may also increase the amount of dissolved organic matter, causing browning of surface water (Kritzberg, 2017;Škerlep et al, 2019) with fundamental consequences for primary production and functioning of aquatic food webs (reviews in Creed et al, 2018;Kritzberg et al, 2020), including changes in the abundance of aquatic invertebrates that are a critical resource for breeding ducks and ducklings (Arzel et al, 2020). Finally, the effects of eutrophication and brownification on aquatic ecosystems may be accelerated by climate change via increased temperature and precipitation and shorter ice duration (Moss et al, 2011;Williamson et al, 2017;Woolway et al, 2020).…”

Changes in wetland habitat use by waterbirds wintering in Czechia are related to diet and distribution changes

“…Invertebrates are fundamental to both terrestrial and aquatic food webs, and drastic decreases have been shown in terrestrial insects on a global level (Dirzo et al., 2014; Wagner et al., 2021). Long‐term studies on aquatic invertebrates are currently scarce (Gozlan et al., 2019), but some indicate changes in aquatic invertebrate community structure (Fried‐Petersen et al., 2020; van der Lee et al., 2021; Pilotto et al., 2020) associated with increasing levels of eutrophication and brownification as one of the most important driver of these changes (Arzel et al., 2020; Jackson et al., 2016; Lind et al., 2018). Fishponds are commercial habitats with artificially managed nutrient input that increases the level of eutrophication (Roy et al., 2020) and are aimed at stocking and breeding fish (mostly carp).…”