Smale DA et al. (2020), Environmental factors influencing primary produ...

ECB-ART-49722

Sci Rep 2020 Jul 22;101:12161. doi: 10.1038/s41598-020-69238-x.

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Environmental factors influencing primary productivity of the forest-forming kelp Laminaria hyperborea in the northeast Atlantic.

Smale DA , Pessarrodona A , King N , Burrows MT , Yunnie A , Vance T , Moore P .

Abstract
Rates and drivers of primary productivity are well understood for many terrestrial ecosystems, but remain poorly resolved for many marine ecosystems, particularly those within in coastal benthic environments. We quantified net primary productivity (NPP) using two methods as well as carbon standing stock within kelp forests (Laminaria hyperborea) at multiple subtidal habitats in the United Kingdom (UK). Study sites spanned 9° in latitude and encompassed a gradient in average temperature of ~ 2.5 °C. In addition to temperature, we measured other factors (e.g. light intensity, water motion, nutrients, sea urchin density) that may influence productivity. Although estimates of NPP were highly variable between sites, ranging from 166 to 738 g C m-2 yr-1, our study-wide average of 340 g C m-2 yr-1 indicated that L. hyperborea forests are highly productive. We observed clear differences between NPP and carbon standing stock between our cold northernmost sites and our warm southernmost sites, with NPP and standing stock being around 1.5 and 2.5 times greater in the northern sites, respectively. Ocean temperature was identified as a likely driver of productivity, with reduced NPP and standing stock observed in warmer waters. Light availability was also strongly linked with carbon accumulation and storage, with increased light levels positively correlated with NPP and standing stock. Across its geographical range, total NPP from L. hyperborea is estimated at ~ 7.61 Tg C yr-1. This biomass production is likely to be important for local food webs, as a trophic subsidy to distant habitats and for inshore carbon cycling and (potentially) carbon sequestration. However, given the strong links with temperature, continued ocean warming in the northeast Atlantic may reduce primary productivity of this foundation species, as optimal temperatures for growth and performance are surpassed.

PubMed ID: 32699214
PMC ID: PMC7376248
Article link: Sci Rep
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References [+] :

Anderson-Teixeira, Carbon dynamics of mature and regrowth tropical forests derived from a pantropical database (TropForC-db). 2016, Pubmed

	Figure 1. Position of study locations and sites along the UK coastline. Left-hand map shows locations (A = north Scotland, B = west Scotland, C = southwest Wales, D = southwest England), right-hand inset maps shows location of each study site within each location. Map produced with ArcGIS 10.3 software (https://www.esri.com/en-us/arcgis/products/index).
	Figure 2. Site-level estimates for NPP relating to (A) lamina extension and (B) regrowth into cleared areas and for (C) carbon standing stock.
	Figure 3. Mean (± SE) values for NPP relating to (A) lamina extension and (B) regrowth into cleared areas and for (C) carbon standing stock for ‘cold’ sites (i.e. A1, A2, B1, B2) versus ‘warm’ sites (i.e. C1, C2, D1, D2). An asterisk indicates significant differences between the cold and warm sites.
	Figure 4. Mean (± SE) values for NPP relating to (A) lamina extension and (B) regrowth into cleared areas and for (C) carbon standing stock for high wave exposure sites versus moderate wave exposure sites (‘n.s.’ indicates non-significant differences).
	Figure 5. Scatterplots showing relationships between carbon-related variables and key environmental variables (see Table S1). Symbols are colour-coded by location as shown in Fig. 1.