Mid-summer vertical behavior of a high-latitude oceanic zooplankton community

Vertical behavior, such as diel vertical migration (DVM) and swarming are widespread among zooplankton. At higher latitudes, synchronized DVM is mostly absent during summer and predominantly herbivorous copepods tend to form large near-surface swarms. This behavior is risky because it can make them vulnerable to visual predators. Here, we used ca. 12 days of mid-summer (28 June to 10 July 2018) high-frequency acoustic data collected on board of an autonomous surface vehicle (Sailbuoy) to study the vertical behavioral patterns of a zooplankton community in the Norwegian Sea (69◦–71◦ N). Comparing acoustic data with zooplankton net samples, we could distinguish the sound scatters into (1). lipid-rich older developmental stages of Calanus spp., (2). younger developmental stages of Calanus spp., smaller copepods and krill and (3). unknown group of strong sound scatters that may have been younger stages of planktivorous fish. We observed shorter-range classic DVM during much of the study period, where in two days, the migration appeared to be pronounced (> 50 m in amplitude), largely synchronous and occurred in the presence of sound scatterer group 3. The observed zooplankton community was concentrated in the upper 20 m in cloudy and calm days but retreated to greater depths at increased near-surface turbulence. This turbulence-driven vertical retreat appeared to be synchronized across the zooplankton community, potentially indicating a schooling behavior

Timing of Calanus finmarchicus diapause in stochastic environments

publishedVersio

Autonomous Surface and Underwater Vehicles as Effective Ecosystem Monitoring and Research Platforms in the Arctic—The Glider Project

Effective ocean management requires integrated and sustainable ocean observing systems enabling us to map and understand ecosystem properties and the effects of human activities. Autonomous subsurface and surface vehicles, here collectively referred to as “gliders”, are part of such ocean observing systems providing high spatiotemporal resolution. In this paper, we present some of the results achieved through the project “Unmanned ocean vehicles, a flexible and cost-efficient offshore monitoring and data management approach—GLIDER”. In this project, three autonomous surface and underwater vehicles were deployed along the Lofoten–Vesterålen (LoVe) shelf-slope-oceanic system, in Arctic Norway. The aim of this effort was to test whether gliders equipped with novel sensors could effectively perform ecosystem surveys by recording physical, biogeochemical, and biological data simultaneously. From March to September 2018, a period of high biological activity in the area, the gliders were able to record a set of environmental parameters, including temperature, salinity, and oxygen, map the spatiotemporal distribution of zooplankton, and record cetacean vocalizations and anthropogenic noise. A subset of these parameters was effectively employed in near-real-time data assimilative ocean circulation models, improving their local predictive skills. The results presented here demonstrate that autonomous gliders can be effective long-term, remote, noninvasive ecosystem monitoring and research platforms capable of operating in high-latitude marine ecosystems. Accordingly, these platforms can record high-quality baseline environmental data in areas where extractive activities are planned and provide much-needed information for operational and management purposes

Mesozooplankton community dynamics in a high arctic fjord

Masteroppgave i marin økologi - Universitetet i Nordland, 201

Simulation of Regression Analysis by an Automated System utilizing Artificial Neural Networks

Artificial Neural Networks have been gaining popularity as statistical tools since it resolves some disadvantages of conventional regression analysis techniques. This paper describes the implementation issues on designing dynamically changing artificial neural networks which are to be applied for the situations where the Regression Analysis is to be used. Furthermore, in order to resolve some of the problems of existing statistical packages like MINITAB, R and SAS, a computer based analysis system is proposed in order to simulate the complete process of building up a regression model and to make future predictions. When implementing the automated system, we used JAVA which supports Object Oriented Programming and MATLAB for easy calculation of mathematical functions. Finally we present a comparative study on the results obtained by the proposed system and the conventional statistical methods. This system provides better output in identifying relationships between independent and dependent variables compared to conventional regression techniques

Mid-summer vertical behavior of a high-latitude oceanic zooplankton community

Vertical behavior, such as diel vertical migration (DVM) and swarming are widespread among zooplankton. At higher latitudes, synchronized DVM is mostly absent during summer and predominantly herbivorous copepods tend to form large near-surface swarms. This behavior is risky because it can make them vulnerable to visual predators. Here, we used ca. 12 days of mid-summer (28 June to 10 July 2018) high-frequency acoustic data collected on board of an autonomous surface vehicle (Sailbuoy) to study the vertical behavioral patterns of a zooplankton community in the Norwegian Sea (69°–71° N). Comparing acoustic data with zooplankton net samples, we could distinguish the sound scatters into (1). lipid-rich older developmental stages of Calanus spp., (2). younger developmental stages of Calanus spp., smaller copepods and krill and (3). unknown group of strong sound scatters that may have been younger stages of planktivorous fish. We observed shorter-range classic DVM during much of the study period, where in two days, the migration appeared to be pronounced (> 50 m in amplitude), largely synchronous and occurred in the presence of sound scatterer group 3. The observed zooplankton community was concentrated in the upper 20 m in cloudy and calm days but retreated to greater depths at increased near-surface turbulence. This turbulence-driven vertical retreat appeared to be synchronized across the zooplankton community, potentially indicating a schooling behavior

Two hundred years of zooplankton vertical migration research

Vertical migration is a geographically and taxonomically widespread behaviour among zooplankton that spans across diel and seasonal timescales. The shorter-term diel vertical migration (DVM) has a periodicity of up to 1 day and was first described by the French naturalist Georges Cuvier in 1817. In 1888, the German marine biologist Carl Chun described the longer-term seasonal vertical migration (SVM), which has a periodicity of ca. 1 year. The proximate control and adaptive significance of DVM have been extensively studied and are well understood. DVM is generally a behaviour controlled by ambient irradiance, which allows herbivorous zooplankton to feed in food-rich shallower waters during the night when light-dependent (visual) predation risk is minimal and take refuge in deeper, darker waters during daytime. However, DVMs of herbivorous zooplankton are followed by their predators, producing complex predator–prey patterns that may be traced across multiple trophic levels. In contrast to DVM, SVM research is relatively young and its causes and consequences are less well understood. During periods of seasonal environmental deterioration, SVM allows zooplankton to evacuate shallower waters seasonally and take refuge in deeper waters often in a state of dormancy. Both DVM and SVM play a significant role in the vertical transport of organic carbon to deeper waters (biological carbon sequestration), and hence in the buffering of global climate change. Although many animal migrations are expected to change under future climate scenarios, little is known about the potential implications of global climate change on zooplankton vertical migrations and its impact on the biological carbon sequestration process. Further, the combined influence of DVM and SVM in determining zooplankton fitness and maintenance of their horizontal (geographic) distributions is not well understood. The contrasting spatial (deep versus shallow) and temporal (diel versus seasonal) scales over which these two migrations occur lead to challenges in studying them at higher spatial, temporal and biological resolution and coverage. Extending the largely population-based vertical migration knowledge base to individual-based studies will be an important way forward. While tracking individual zooplankton in their natural habitats remains a major challenge, conducting trophic-scale, high-resolution, year-round studies that utilise emerging field sampling and observation techniques, molecular genetic tools and computational hardware and software will be the best solution to improve our understanding of zooplankton vertical migrations

Seasonal vertical strategies in a high-Arctic coastal zooplankton community

We studied the larger (>1000 µm) size fraction of zooplankton in an Arctic coastal water community in Billefjorden, Svalbard (78°40’ N), Norway, in order to describe seasonal vertical distributions of the dominant taxa in relation to environmental variability. Calanus spp. numerically dominated the herbivores; Aglantha digitale, Mertensia ovum, Beroë cucumis, and Parasagitta elegans were the dominant carnivores. Omnivores and detritivores were numerically less important. Descent to deeper regions of the water column (>100 m) between August and October, and ascent to the shallower region (<100 m) between November and May was the overall seasonal pattern in this zooplankton community. In contrast to other groups, P. elegans did not exhibit pronounced vertical migrations. Seasonal vertical distributions of most species showed statistical associations with the availability of their main food source. The vertical distribution of later developmental stages of Calanus spp. was inversely associated with fluorescence, indicating that they descended from the shallower region while it was still relatively productive, and ascended before the primary production had started to increase. Strong associations between the vertical distributions of secondary consumer M. ovum and Calanus spp., and tertiary consumer B. cucumis and M. ovum indicated that these carnivores seasonally followed their prey through the water column. We conclude that seasonal vertical migrations are a widespread trait in the high Arctic community studied, and predator−prey interactions seem particularly central in shaping the associations between the seasonal vertical strategies of adjacent trophic levels