Working on a baseline for the Kongsfjorden food web: production and properties of macroalgal particulate organic matter (POM)

Abstract

Macroalgae, in particular kelps, produce a large amount of biomass in Kongsfjorden, which is to a great extent released into the water in an annual cycle. As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 % of the blade area per day (August 2012), thereby adding to the pool of particulate organic matter (POM) in the fjord. Upon release small thallus pieces are ''aging'' in that they are prone to leaching and serving as substrate for microorganisms, thus turning into palatable food for suspension and bottom feeders. In order to define a macroalgal baseline for the Kongsfjorden food web, stable isotopes d 14 C and d 15 N were measured in individuals of A. esculenta, Saccharina latissima and Laminaria digitata directly sampled after collection and in artificially produced POM (aPOM) of A. esculenta that was allowed to age under experimental conditions. In aPOM from this species sampled in August 2012 the C/N ratios decreased between d1 and d8 of a 14-day culture period in parallel to the fading photosynthetic activity of the algal fragments as demonstrated by use of an Imaging-PAM. Microscopic observations of the aPOM in August 2012 and 2013 revealed the frequent occurrence of small brown algal endo-and epiphytes. First feeding experiments with Mysis oculata (Mysids) and Hiatella arctica (Bivalves) showed that these species can ingest macroalgal POM. The importance of kelp-derived POM for the food web is subject of the current research.

Ecosystem Kongsfjorden: new views after more than a decade of research

“…As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 % of the blade area per day during the autumn (2012), thereby adding to the pool of particulate organic matter (POM) in the fjord (Buchholz and Wiencke 2015). This is interesting because in their preliminary feeding experiment, the mysid Mysis oculata was shown to ingest artificially produced POM (aPOM) from Alaria esculenta, and ingestion of aPOM was also demonstrated in the bivalve Hiatella arctica.…”

“…They detected no consistent differences in meio-and macrofaunal density, diversity or composition during the year, although possible responses to spring food supply in meiofaunal reproduction were observed in Nematoda, Harpacticoida and macrobenthic Crustacea. They concluded that the resilience of the benthic community to marked seasonality in pelagic phytodetritus fluxes may be related to organic matter reserves in sediments, inclusion of macroalgal carbon into the diet (see also Buchholz and Wiencke 2015) and employment of lecitotrophic larva or direct development by polar benthos.…”

Characterizing energy flow in kelp forest food webs: a geochemical review and call for additional research

“…−1.5‰ to 1.5‰), and generally fall within the range of live kelps (Fig. 6; Stephenson et al 1986, Markel and Shurin 2015, Buchholz and Wiencke 2016, Buchholz et al 2019, Gabara 2020. We suspect this is the main route through which kelp-derived energy supports consumers for two reasons.…”

Metagenomic Analysis of The Effects of Salinity On Microbial Diversity and Functional Gene Diversity in Kongsfjorden Estuary

“…The high abundance of the former due to the fact that this bacterium prefers to utilize complex organic matter by directly attaching to algal cells and algal derivative clastic particles (Y. Li et al 2018), while the fresh water of S5 is more conducive to the growth of algae (Buchholz Wiencke 2016), so salinity indirectly affects the abundance of Flavobacteriaceae. The high abundance of Vibrionaceae can be ascribed to its association with soil microbiota (Reen et al 2006), suggesting that Vibrionaceae may be terrigenous microorganism, which are imported into the fjords by glacial meltwater and are subjected to salinity stress, which is not so abundant in high-salinity areas.…”