Biogeochemical effects of macroalgal decomposition on intertidal microbenthos: a microcosm experiment

Abstract

The decomposition of macroalgal detritus (tubular and planar Ulva spp.) was studied in a microcosm under a daily light:dark cycle to simulate the decomposition on intertidal sediment. The consequences of bloom decay were evaluated in the bulk water phase and in the sediment. ), dissolved organic carbon (DOC) and inorganic carbon (DIC) were measured in the inflowing and outflowing seawater. Vertical microprofiles of O 2 , pH and H 2 S at the sediment -water interface, sediment contents of organic matter (OM), inorganic and organic carbon (C org ), total nitrogen (N) and inorganic nutrients were measured before and after addition of macroalgal detritus. Changes in the taxonomic composition of microphytobenthos were studied by optical microscopy and by the analysis of photosynthetic pigments. Macroalgal detritus vanished from the sediment surface in 6 d. Macroalgal decomposition shifted the microcosm net balance to higher releases of DOC, DIC and inorganic nutrients, suggesting rapid release from macroalgal biomass. Besides being released to the water column, a fraction of macroalgal carbon and of nitrogen was incorporated into the sediment as indicated by a transient increase in C org and N. Aerobic mineralization of macroalgal detritus reduced O 2 in the water column and the sediment. Microbenthos photosynthetic activity was initially suppressed but recovered from the third day as macroalgal detritus decomposed. Photosynthetic O 2 production by microbenthos largely determined the fraction of macroalgal detritus that was aerobically mineralised. Decomposition of macroalgal detritus favoured the dominance of cyanobacteria over diatoms in the microbenthos. KEY WORDS: Macroalgal blooms · Microbenthos · Microelectrodes · Macroalgal decomposition · Macroalgal detritusResale or republication not permitted without written consent of the publisher

Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community

“…On the other hand, our estimate may have been conservative if hydrodynamic mixing of the sediment surface entrains macroalgae into the sediments. In either case, it is clear from other laboratory and field studies that some fraction of macroalgae associated with blooms is transferred to the sediments following die-off , Lomstein et al 2006, García-Robledo et al 2008. We suggest that further research investigating the influence of hydrodynamic forcings and sediment resuspension on macroalgal decomposition in the sediments is warranted.…”

“…Mar Ecol Prog Ser 414: [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] 2010 Studies of macroalgal bloom decay have demonstrated rapid breakdown of biomass, resulting in release of both inorganic and organic nutrients to the water column (Buchsbaum et al 1991, Castaldelli et al 2003, García-Robledo et al 2008, supporting phytoplankton and bacterial metabolism , Nedergaard et al 2002. Fewer studies have focused on macroalgal decay within the sediments (Nedergaard et al 2002, Lomstein et al 2006, Rossi 2007, García-Robledo et al 2008, where heterotrophic bacterial densities are significantly higher than in the water column (Deming & Baross 1993, Schmidt et al 1998, Ducklow 2000.…”

The effect of mechanical pre-processing and different drying methodologies on bioethanol production using the brown macroalga Laminaria digitata (Hudson) JV Lamouroux

“…Instead, it is hypothesised that the decrease in ethanol yields is due to a loss of soluble laminarin and glucose during the defrosting process prior to cutting the kelp strips to the average particle size. As García-Robledo et al (2008) notes in their work on the biogeochemical effects of macroalgal decomposition, there is little work on algal decay with most focussing on the degradation of the macroalgal tissue rather than the residues. However, approximately half of the laminarin content of kelps is soluble (Nelson and Lewis 1974), and previous work by the authors (Adams et al 2015) has demonstrated that a brief washing of kelp with tap water can remove up to 49% of the laminarin present.…”

Artificial Top Layer Sediment Resuspension To Counteract Chaetomorpha Linum (Muller) Kutz Blooms In A Eutrophic Lagoon. Three Years Full-Scale Experience

“…If the Chaetomorpha linum mat grows within about the first 20 cm, the underlying part does not carry out photosynthesis and is subject to bacterial attacks [35], to the point that the last decimeter of the mat thickness decays and produces organic mud on the bottom, enriching the sediment in carbon and nitrogen [36] and producing effects on microbial community and processes [37]. The anaerobic mineralization that occurs at the sedimentwater interface releases inorganic nutrients toward the water column [38], such as ammoniun (NH 4 + ) [39], and carbon dioxide (CO 2 ) and orthophosphate (PO 4 3-) [40].…”