Micronutrients and mangroves: Experimental evidence for copper limitation

Abstract

Testing the availability and requirements of micronutrients during early mangrove growth is essential for understanding their recruitment success across intertidal gradients. Recent research has highlighted the role of dissolved iron in mangrove growth, but the role of other trace metals (Cu, Zn, Mo) in supporting and possibly limiting tree growth is unknown. In outdoor experiments, dissolved copper, supplied at a rate mimicking those in natural forests, limited early growth of five species of mangroves. Rates of stem extension and biomass increase from seedling to sapling stage of Rhizophora apiculata, Bruguiera gymnorrhiza, Avicennia marina, and Ceriops tagal increased linearly with increasing rates of Cu supply (0.0 μmol m−2 d−1, 0.005 μmol m−2 d−1, 0.01 μmol m−2 d−1, 0.02 μmol m−2 d−1, and 0.05 μmol m−2 d−1); early growth of Xylocarpus moluccensis best‐fit Gaussian curves with maximal growth at a Cu supply rate of 0.02 μmol m−2 d−1 with toxicity evident at the highest Cu supply rate. Most copper was stored in roots and leaves. Zinc and molybdenum were not limiting for growth of any of the five species, but X. moluccensis growth declined with increasing Mo supply, suggesting lower tolerance and greater toxicity. Differences in such requirements among species, especially during early establishment, may be a key driver in fostering changing patterns in species composition among forests.

Impact of Global Change on Nutrient Dynamics in Mangrove Forests

“…Owing to their estuarine and marine existence, mangroves are generally not limited by the relatively large quantities of sulfur, boron, potassium, magnesium, and sodium in seawater but are frequently limited by nitrogen and phosphorus. Iron and copper have been found to be limiting for mangroves in mesocosm studies [11,12]. The critical need for nitrogen and phosphorus has been repeatedly demonstrated in field and laboratory studies [9].…”

“…Experiments by Reef et al [49] show that the effects of CO 2 on mangrove growth are more greatly enhanced in the presence of additional nutrients, which is high nutrient availability. Conversely, a decline in mangrove growth will probably translate into decreased utilization and a possible buildup of dissolved soil nutrients, which is similar to the buildup of soil ammonium when mangroves are deforested [12]. Most nitrogen and phosphorus will likely remain immobilized.…”

Zinc isotopes as tracers of anthropogenic sources and biogeochemical processes in contaminated mangroves

“…Essential elements (e.g., Zn, Cu, Mo) play an important biological role and participate in a wide range of important cellular biochemical reactions (Reilly, 2004). At high M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT concentrations, however, these elements lead to reduction of photosynthesis in mangrove plants and of growth and biomass, and finally induce mortality (Adriano and Adriano, 2001;Sparks, 2005;Bayen et al, 2012 and references therein;Alongi, 2017).…”

Mangroves in arid regions: Ecology, threats, and opportunities

“…In the Red Sea, soil P was also relatively low, with values ranging between 0.03 and 0.08 % (Saderne et al, 2020). Due to the presence of carbonates in many arid coasts, P is likely to precipitate and become inaccessible for plant uptake and become an essential limitation for mangrove growth (Alongi, 2017). Even where nutrient enrichment may be intense, it may not be sufficient to stimulate growth in arid regions where high salinity limits mangrove productivity (Naidoo, 2009;Lovelock et al, 2011;Almahasheer et al, 2016).…”