Biophysical Interactions in Fragmented Marine Canopies: Fundamental Processes, Consequences, and Upscaling

Abstract

Spatial fragmentation is a near-ubiquitous characteristic of marine canopies. Biophysical interactions with fragmented canopies are multi-faceted and have many significant implications at multiple scales. The aims of this paper are to review research on biophysical interactions in fragmented marine canopies, identify current gaps in knowledge and understanding, and propose ways forward. The review starts at the patch/gap scale and focuses initially on hydrodynamic interactions. It then considers the consequences of these interactions for particulate and dissolved material, and distributions of canopy-associated organisms. Finally, it addresses issues of upscaling to landscape-scale and ways in which this research can be applied to marine landscape management. Work on a broad range of canopy types is considered, including micro-algal biofilms and turf algae; macro-algae, seagrasses and coral reefs; saltmarsh vegetation and mangroves. Although the focus is on marine canopies, insights from studies of fragmented canopies in other contexts are drawn on where relevant. These include freshwater environments and terrestrial forests, grasslands, crop canopies, and urban areas. Specific areas requiring greater attention are highlighted. As a result of this meta-analysis, the following recommendations are made for further research. A lack of basic data is identified across all canopy types regarding the formation, fate and spatial and temporal characteristics of canopy patches, gaps, and spatial structure. Studies of hydrodynamics with fragmented canopies would benefit from shifting focus toward more non-uniform, realistic configurations, while ecological research in this area would benefit from a move toward configurations that are more controlled and tractable for quantitative modeling. More comparative studies across canopy types would enable understanding of their biophysical interactions and their consequences to be more fully tested and developed. A greater incorporation of chemical aspects of canopy systems into work that has hitherto focused on biophysical interactions would also be pertinent. Upscaling of patch and gap-scale phenomena to landscape-scale is identified as a crucial topic, since it is at the latter scale that management efforts are most readily carried out. Overall, an approach that balances hydrodynamics, marine canopy ecology, spatial analysis of landscapes, biogeochemistry, and socio-environmental interactions is recommended.

A Convolution Method to Assess Subgrid‐Scale Interactions Between Flow and Patchy Vegetation in Biogeomorphic Models

“…Kleinhans et al, 2015;Kearney & Fagherazzi, 2016;Kirwan et al, 2016;Caponi & Siviglia, 2018;Schwarz et al, 2018;Lauzon & Murray, 2018;Piliouras & Kim, 2019). There is field evidence that, for some vegetation species, early stage of colonization can occur in heterogeneous patterns of small-scale vegetation patches (order of m 2 - Bouma et al, 2007;Van der Wal et al, 2008;Balke et al, 2012;Nepf, 2012;van de Vijsel et al, 2020) which are known to have important impacts on the biogeomorphic developments at the landscape scale (order of km 2 - Folkard, 2019;Larsen, 2019). Prominent examples are the formation of channel networks by differential erosion and deposition patterns (Temmerman et al, 2007;Schwarz et al, 2018;Taramelli et al, 2018) and the heterogeneous development of larger vegetated landforms (Chen et al, 2012;Follett & Nepf, 2012;Gurnell, 2014).…”

The World of Edges in Submerged Vegetated Marine Canopies: From Patch to Canopy Scale

“…Micro-canopies refer mainly to permeable vegetation forming a patch, whereas a classic marine canopy refers to a permeable region forming a canopy. In both cases, the canopies are made of highly flexible elements that pronate in the direction of the flow and oscillate back and forth in response to wave forcing [57].…”

“…The study focuses on the edges and limits of submerged marine seagrasses, saltmarshes, and seaweeds. They are made of highly flexible elements pronating in the direction of the flow and oscillating back and forth in response to wave forcing [57] and present edges with a frontal area separating the vegetation from the adjacent non-vegetated zones [52].…”

“…Searches were carried out for manuscripts that included in their titles, abstracts or keywords, the key words in combination and beginning with "meadow" OR "canop" AND "marine" OR "sea" AND "edge" OR "boundar" OR "patch" OR "margin" OR "front" OR "upper limit" OR "shallow limit" OR "lower limit" OR "deep limit" OR "fringe". For each word, wildcard asterisks were added to the end so that plurals and other related words would be found, i.e., canop* would pick up the words of canopy and canopies [57]. This search produced hundreds of results that were then filtered by the authors' subjective analysis and by considering those carried out during the last 30 years (1991 as the start date and 2021 as the end date).…”

Scale-dependent effects of vegetation on flow velocity and biogeochemical conditions in aquatic systems

“…In streams, submerged plants typically grow in patches (Fig. 1; Sand-Jensen and Madsen, 1992) and affect ecosystem processes (Carpenter and Lodge, 1986) by modifying flows and sediment dynamics (Wharton et al, 2006;Folkard, 2019). Patches are porous structures through which flow can partially pass, but with a reduced velocity relative to the upstream conditions (Sand-Jensen and Pedersen, 2008;Folkard, 2011;Vandenbruwaene et al, 2011;Nepf, 2012;Marjoribanks et al, 2017;Licci et al, 2019), which causes the flow to deflect and accelerate above and next to the canopy, locally increasing water velocity and turbulence at the edges of the patch (Sand-Jensen and Mebus, 1996;Sand-Jensen and Pedersen, 2008;Sukhodolov and Sukhodolova, 2010;Folkard, 2019).…”