Characterization of the biological, physical, and chemical properties of a toxic thin layer in a temperate marine system

Abstract

The distribution of plankton in the ocean is patchy across a wide range of spatial and temporal scales. One type of oceanographic feature that exemplifies this patchiness is a ‘thin layer’. Thin layers are subsurface aggregations of plankton that range in vertical thickness from centimeters to a few meters, which may extend horizontally for kilometers and persist for days. We undertook a field campaign to characterize the biological, physical, and chemical properties of thin layers in Monterey Bay, California (USA), an area where these features can be persistent. The particle aggregates (marine snow) sampled in the study had several quantifiable properties indicating how the layer was formed and how its structure was maintained. Particles were more elongated above the layer, and then changed orientation angle and increased in size within the layer, suggesting passive accumulation of particles along a physical gradient. The shift in particle aggregate orientation angle near the pycnocline suggests that shear may also have played a role in generating the thin layer. Pseudo-nitzschia spp. were the most abundant phytoplankton within the thin layer. Further, both dissolved and particulate domoic acid were highest within the thin layer. We suggest that phosphate stress is responsible for the formation of Pseudo-nitzschia spp. aggregates. This stress together with increased nitrogen in the layer may lead to increased bloom toxicity in the subsurface blooms of Pseudo-nitzschia spp. Several zooplankton groups were observed to aggregate above and below the layer. With the knowledge that harmful algal bloom events can occur in subsurface thin layers, modified sampling methods to monitor for these hidden incubators could greatly improve the efficacy of early-warning systems designed to detect harmful algal blooms in coastal waters.

Plankton Genes and Extracellular Organic Substances in the Ocean

“…In many other consortia, such as biofilms [50][51][52], lake and marine organic aggregates [53,54], however, cohesion is achieved by physical processes such as stickiness [55], gelling [56] or increased viscosity [57], mediated by exopolymeric substances (EPS). Schwartz et al [33] suggested that consortia with more elements than 3 are likely to exist, but that the number of degrees of freedom would make their existence difficult to prove.…”

Edge computing at sea: high-throughput classification of in-situ plankton imagery for adaptive sampling

“…Algal thin layers are often highly transient in location and persistence. While their presence may be predictable in some situations (e.g., Greer et al, 2013;Greer et al, 2020;McManus et al, 2021), actual encounter of them may be a chance occurrence, and indication of their presence may be vague (e.g., Chl a signal appearing highly noisy). Verifying the presence, and detailing the vertical distribution of organisms associated with a thin layer can only be done with focused vertical sampling.…”

Cells of matter and life – towards understanding the structuring of particles and plankton patchiness in the Arctic fjords

“…But more generally neither the distribution patterns nor the concentrations of most of the size fractions correlated significantly with chlorophyll, which suggests that some of those concentration hotspots did not consist of actively fluorescent particles or plankton. The significant correlation got for the Large size fraction in ISF (Supplementary Figure 5) could indicate either the fluorescent nature of marine aggregates (Timmerman et al, 2014;Graff and Menden-Deuer, 2016;McManus et al, 2021), or the spatial match between herbivorous grazers [as the Large fraction is mostly represented by Calanus copepods (Balazy et al, 2018;Balazy et al, 2019)] and food stocks (expressed as high chlorophyll levels).…”