Estimating Nitrogen and Phosphorus Cycles in a Timber Reef Deployment Area

Abstract

In an oligotrophic bay, Mitsu Bay, Japan, artificial timber reefs (ATRs) are deployed to increase fish production. In such man-made ecosystems, the biological activities of other organisms as well as the physical structures of ATRs could influence nutrient cycling. A pelagic–benthic coupling model expressing both phosphorus and nitrogen cycling was developed to investigate seasonal variation in the associated nutrients and their annual budget in the ATR areas and the entire bay system. The model consists of equations representing all the relevant physical and biological processes. The model reproduced the observed seasonal variations in dissolved inorganic P, ammonium, and nitrate concentrations that were low in spring and summer and high in autumn and winter. The internal regeneration rates of the nutrients were two times higher in the ATRs than in the bay area, so that fish production was predicted to be higher in the ATRs than in the bay area. Considering the inflows from the land and precipitation are quite low, nutrient regeneration is an important source of nutrients for the water in Mitsu Bay. ATR deployment could be an important local nutrient source in an oligotrophic bay, and could increase fish production.

Who lives in a pear tree under the sea? A first look at tree reefs as a complex natural biodegradable structure to enhance biodiversity in marine systems

“…Similar to other experimental studies introducing geogenic or biogenic hard substrates into soft-sediment coastal ecosystems (Alam et al, 2020) we found that the tree-reefs quickly developed into hotspots of sessile epibenthos biodiversity. Notably, we found a clear vertical zonation of species over the reefs' vertical gradient.…”

“…Historically, large wood has been removed from river systems globally (Nagayama and Nakamura, 2010) though it is well documented that large woody debris creates excellent habitat for fish in aquatic systems (McMahon and Holtby, 1992) such as rivers, lakes, and estuaries. This is also found to be the case in marine environments (Gonor et al, 1988;Masuda et al, 2010;Alam et al, 2020). However, studies on the effect of large woody debris on fish and sessile life in marine systems are very limited in comparison with studies on the biological effect of wood in riverine and estuarine environments.…”

“…In the case of tires and some metallic structures, toxic substances leaching from these reefs has proven to negatively affect the biota (Aleksandrov et al, 2002;Lima et al, 2019). Wood, even if treated, is a highly suitable substrate for epifaunal assemblages (Brown, 2005), and wooden artificial reefs are colonized significantly more quickly by more species and larger fish than alternatives such as PVC or steel (Masuda et al, 2010;Alam et al, 2020).…”

“…Whereas the use of wood to create reef-like structures has been well established in freshwater systems like rivers and lakes (Lehane et al, 2002;Whiteway et al, 2010), to our knowledge only few such studies have been conducted in marine environments (Lima et al, 2019). These studies show that wooden reefs undergo rapid colonization and increased fish use compared to traditional artificial reef material such as concrete (Chapman and Clynick, 2006;Alam et al, 2020). Previous work on wood reintroduction within rivers has demonstrated a positive increase in fish habitat in areas with wood placement, leading to a large increase in fish biomass and density (Lehane et al, 2002;Whiteway et al, 2010).…”

Advances on Water Quality Detection by UV-Vis Spectroscopy

“…If the discharge exceeds the standard, the balance of the water body will be destroyed, resulting in rapid algae and plankton growth in the water body. The decrease in concentration and the death of fish and shrimp in a large area will eventually worsen the water quality, thus affecting human production activities in the ocean [59].…”