Marine environments are changing, and further changes are expected in response to climate change, industry development (e.g. oil and gas explorations and marine renewable energy), pollution, and overfishing. There is an urgent need to understand effects of these stressors on marine ecosystems and to adopt effective management measures that minimize detrimental effects. Accomplishing this goal requires a comprehensive understanding of “natural” temporal patterns of biological components and underlying processes. High-latitude environments and marine renewable energy development sites have been particularly understudied due to sampling challenges (e.g. presence of sea ice, and high currents). This lack of baseline information required to measure biological responses to environmental change has increased the difficulty to document impacts in these areas and to predict effects of further changes in the ecosystems. Chapter 1 reviews temporal variability in marine ecosystems. Chapters 2 and 3 evaluate high resolution, stationary acoustic data from the Chukchi Ecosystem Observatory (CEO) and concurrent measurements from a large set of environmental sensors to characterize temporal variability in the abundance and behavior of fish and zooplankton in the Chukchi Sea. Chapter 4 quantifies the spatial area that is represented by acoustic point source measurements to define the spatial scope of CEO observations and to inform cost-effective monitoring design at high latitudes. Chapter 5 compares temporal variability in biological characteristics at sites selected for wave and tidal energy industry development to assess the potential for applying standard methods and analytic tools for biological monitoring. Chapter 6 provides a synthesis of results and implications for biological monitoring. This comprehensive characterization of fish and zooplankton dynamics in the Chukchi Sea and at sites selected for marine renewable energy development increases our ability to detect and predict biological responses to environmental change, ensure the collection of representative samples, and assist in the design of standard strategies for biological monitoring at a range of aquatic ecosystems.