Seven ecological and technical attributes for biofilm‐based recovery of shorebird populations in intertidal flat ecosystems

Abstract

1. Soft-bottomed intertidal flats are essential foraging areas for shorebirds but are severely impacted by threats such as coastal development and climate change.Notwithstanding the urgency for humanintervention (conservation, restoration and creation) of tidal flats, few ecologically based technical guidelines exist for the artificial (clearly intended human intervention) intertidal flats, and none explicitly consider the unique properties of intertidal biofilm as a critical food source for small-bodied shorebirds.2. We propose that effective human intervention in intertidal flat ecosystems can be developed through mirroring the needs of small-bodied shorebirds. Scientific evidence from intertidal flat recovery projects in Japan is summarized, and foraging requirements of shorebirds are reviewed with a focus on intertidal biofilm as a critical food source.3. These findings are used to propose the primary goal of intervention, that is maximizing total energy intake for population recovery of small-bodied shorebirds through biofilm. Three sub-goals are presented for creating environmental conditions in which (1) a broad spectrum of food sources is available, but particularly intertidal biofilm; (2) maximizing energy intake rate per individual; and (3) maximizing foraging activity. We then describe seven key ecologically based technical attributes for artificial intertidal flats that promote use by small-bodied shorebirds: depositional environment, complex shoreline, gentle slope, gradient of grain sizes from muddy to sandy, maximum water depth at the lowest tide 5 cm or less, freshwater inflow and unobstructed sight-lines. 4. Critical questions remain for effective intervention in intertidal flat ecosystems, including food web dynamics, variation in the quality and quantity of food sources, especially biofilm, optimal sedimentary environment systems (interaction between grain size, bed slope and elevation), monitoring involving comparisons with appropriate benchmark (control) habitats, quantifying foraging behaviour and the synergy and trade-offs among ecosystem services.

Landscape changes in a critical subtropical coastal wetland in northwestern Mexico: Is shrimp farming a driver of concern?

“…According to the o cial statistics for the municipality of Angostura, which includes most of the BSMR wetland system, the social impacts of shrimp farming are di cult to assess, especially considering recent methodological changes to measure poverty and well-being in Mexico. Even so, the number of people in poverty in Angostura decreased from 48% in 2010 to 26% in 2020, although this reduction was accompanied by a decrease in population size of 14 in saltmarshes threatens various biological and biogeochemical processes, such as the vertical and horizontal migrations of benthic microalgae, and benthic-pelagic coupling that supports high primary productivity and sustains food webs (Kuwae et al, 2021;Lebreton et al, 2019). Coastal wetlands, such as saltmarshes and mangroves, may also be responsible for ~ 50% of the carbon that is sequestered each year in the oceans (Adam, 2019).…”

Biofilm and invertebrate consumption by western sandpipers (Calidris mauri) and dunlin (Calidris alpina)during spring migratory stopover: insights from tissue and breath CO2 isotopic (δ13C,δ15N) analyses

“…In doing so, recent studies into western sandpiper use of intertidal biofilm in the Fraser River estuary offer hope on how deeper appreciation of physiological requirements can boost understanding of shorebird migration generally and better inform conservation (Schnurr et al, 2018, Schnurr et al, 2020 ; Canham et al , 2021 ). In summary, given rapidly increasing anthropogenic threats, isotopic tissue and breath methodology offers a critical new tool to understand how spatio-temporal patterns in the biofilm ‘landscape’ align with the physiological demands of migrating shorebirds and a means to more effective conservation and restoration for stopover sites globally ( Kuwae et al , 2021 ).…”

Shorebird Abundance is Associated with Nutritional Quality of Intertidal Biofilm on the Fraser River Estuary

“…Spatial differences in macronutrient content, particularly lipids, demonstrate the need to consider the nutritional "quality" of biofilm and not just biomass (i.e., chlorophyll a) when determining restoration goals for tidal flats or assessing coastal areas for development projects. The technical attributes for artificial intertidal flats that promote use by small-bodied shorebirds include a depositional environment, complex shoreline, gentle slope, gradient of grain sizes from muddy to sandy, maximum water depth at the lowest tide 5 cm or less, freshwater inflow, and unobstructed sight-lines (Kuwae et al 2021). However, several critical questions remain for effective intervention in intertidal flat ecosystems, including the provision of essential nutrients during key periods in the life cycle of shorebirds.…”