Community composition in mangrove ponds with pulsed hypoxic and acidified conditions

Abstract

The potential resilience of biological communities to accelerating rates of global change has received considerable attention. We suggest that some shallow aquatic ecosystems, where temperature, dissolved oxygen (DO), and pH can exhibit extreme variation on short timescales of hours or days, provide an opportunity to develop a mechanistic understanding of species persistence and community assembly under harsh environmental conditions. Extreme diel swings in DO and pH have been observed in eutrophic temperate ecosystems, and here, we describe a similar phenomenon consistently occurring across tropical sites that included relatively remote atolls on the Meso‐American barrier reefs in Belize and oligotrophic coastal lagoons in Panama. In particular, we documented large daily swings in temperature, DO, and pH within shallow ponds of Caribbean mangrove forests. Water in seven of 13 ponds went hypoxic (<2 mg/L DO) during the multiday sampling period, and pH dipped nightly to low levels, falling below 7.0 in some ponds. Minimum pH and minimum DO were correlated, and showed a similar relationship in Belize and Panama, suggesting a common mechanism produced diel cycles. Remarkably, most ponds exhibited high abundance of macroalgae, macroinvertebrates, and fish, despite potentially stressful abiotic conditions. Although fish diversity was negatively correlated with pH range, our overall results from the ponds suggest that many species are sufficiently resistant such that a functionally complex community can persist in the midst of pulsed stressful conditions. We propose that the mangrove ponds could serve as a model ecosystem for investigating resistance and resilience of coastal marine communities to global change factors such as climate change, hypoxia, and ocean acidification.

Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

“…However, the associated risk of hypoxia in the study system was still to be tested. Diel hypoxia conditions observed in other mangrove systems (Knight et al, 2013;Dubuc et al, 2017;Gedan et al, 2017;Mattone and Sheaves, 2017) were also a seemingly common condition in Bouraké. DO showed extreme and rapid fluctuations with the diel and tidal cycles.…”

“…Low DO was recorded daily and was most severe during nighttime ebbing tide, reaching levels that can compromise fish fitness (Rogers et al, 2016). It is likely that hypoxia is a common condition of intertidal mangrove forests due to the mineralisation of a large amount of organic matter produced by mangrove trees, responsible for a high consumption of oxygen by bacteria (Alongi et al, 2004;Dittmar et al, 2006), but also due to the exchange of porewater between sediments and the water column, known as "tidal pumping" (Li et al, 2009;Gleeson et al, 2013;Call et al, 2015;Leopold et al, 2017). Briefly, at each flooding tide, water infiltrates intertidal sediments and then drains back to the water column during the next ebbing tide, while in the sediments, water becomes enriched in reduced compounds such as NH 3 , H 2 S and FeS 2 , resulting in water acidification and deoxygenation (Marchand et al, 2011).…”

“…DO is crucial for all aerobic organisms, including fish (Driedzic and Hochachka, 1978;Falkowski and Raven, 1997). However, DO availability varies extremely over the tidal and diel cycle in mangrove habitats, reaching levels that can lead to physiological stress (Knight et al, 2013;Dubuc et al, 2017;Gedan et al, 2017;Mattone and Sheaves, 2017). Consequently, it is likely that some fish species respond to changes in DO by undertaking tidal migrations or by avoiding mangrove forests permanently to prevent the adverse effects following exposure to low DO.…”

The influence of physicochemical environment on the distribution and abundance of mangrove gastropods in Ngurah Rai Forest Park Bali, Indonesia

“…The difference in DO concentration was due to the location of the observations that were close to residential areas, tourism, and businesses center to produce anthropogenic waste. Gobler and Baumann (2016); Gedan et al (2017); Farooq and Siddiqui (2020), states that DO concentration will decrease if the waters are polluted by waste without any prior processing.…”

Hypoxia in mangroves: occurrence and impact on valuable tropical fish habitat

“…DO is crucial for all aerobic organisms, including fish (Driedzic and Hochachka, 1978;Falkowski and Raven, 1997). However, DO availability varies extremely over the tidal-and diel-cycle in mangrove habitats, reaching levels that can lead to physiological stress (Knight et al, 2013;Dubuc et al, 2017;Gedan et al, 2017;Mattone and Sheaves, 2017). Consequently, it is likely that some fish species respond to changes in DO by undertaking tidal migrations, or by avoiding mangrove forests permanently to prevent the adverse effects following exposure to low DO.…”