Invasive Aquatic Species

Freshwater ecosystems are particularly susceptible to invasions by invasive non-native species (INNS) across a range of taxa, largely as a consequence of anthropogenic influences on these systems, with a number of ecological and socio-economic impacts. This chapter reviews freshwater invasive non-native species across the globe, focusing on fishes, invertebrates, floating macrophytes, and submerged macrophytes emphasising the knowledge gaps in particular that have resulted in biases inherent in assessments of freshwater invasions. These include an ecological bias because the majority of studies focus on terrestrial invasions; a geographical bias as most studies are focused on temperate northern hemisphere systems; and a taxon bias where fish invasions, populate the literature. This chapter highlights some of the approaches needed to survey, monitor, and manage INNS.

Secondary Data

Understanding biodiversity change and addressing questions in freshwater management and conservation requires access to biodiversity data and information. Unfortunately, large, comprehensive data sources on freshwater ecology and biodiversity are largely lacking. In this chapter, we explain how to take advantage of secondary data and improve data availability for supporting freshwater ecology research and biodiversity conservation. We emphasise the importance of secondary data, give an overview of existing databases (e.g., taxonomy, molecular or occurrence databases), discuss problems in understanding and caveats when using such data, and explain the need to make primary data publicly available.

Changes Over Time

Freshwater systems are continuously shaped by cyclical and directional forces of change, whether they be natural or anthropogenic. Beyond gradual transitions disturbances can reset their internal dynamics generating an abrupt ecological shift. Long-term data sets of gradual or abrupt change can be accessed by exhuming the physical, chemical, and biological remains archived in the sediment layers within lakes and wetlands. Long-term monitoring programmes offer more detailed evidence, usually over shorter time frames. In combination these records attest to the response of wetlands to climate and the impact of industrialised people. Humans have modified lake ecosystems for millennia and the condition of many wetland ecosystems have changed such that they are now regarded as novel. Long-term records provide targets for wetland restoration and can identify the main drivers of degradation. Identification of the character of modern Ramsar wetlands may be enhanced by reference to records of past state.

Freshwater Vertebrates

Freshwater habitats are vitally important for vertebrate diversity and ecosystem service provision. These habitats are diverse in scale and type, ranging from vast wetlands and tropical flooded forests to small streams and ponds, but are all equally important to the diverse range of vertebrates they support. The loss and degradation of freshwater habitats globally, largely driven by agricultural intensification, land-use change and deforestation, threatens vertebrates and the continued functioning of freshwater ecosystems. Well-informed, evidence-based conservation is reliant on suitably designed surveys capable of detecting population changes in target species. Due to the diversity and complexity of freshwater habitats and their associated vertebrate taxa a comprehensive review of all methods for all species is beyond the scope of this chapter. However, here we outline key considerations and methods for surveying vertebrates in freshwater systems and provide signposts to relevant case studies and resources to help plan successful monitoring programmes for freshwater vertebrates.

Chemical Determinands of Freshwater Ecosystem Functioning

Chemical equilibria in surface waters stem from complex interactions between physical background and living components of ecosystems. Catchments differ in geological background, climate, and land use; their run-off bears a distinctive chemical ‘fingerprint’. This chapter illustrates how the monitoring of standard parameters, such as oxygen, pH, conductivity, major ions, nutrients, and carbon, can lead to an interpretation of key aspects of the functioning of major ecosystem processes and how chemical constituents may affect the distribution of aquatic organisms. This requires understanding principles that underlie available measurement techniques and it demands a certain familiarity with the intrinsic variability of parameter values and of their chemical interaction. It is not required that field scientists be able to conduct detailed chemical assessments, but all should be able to collect samples yielding high-quality data. Therefore, detailed advice on chemical monitoring practice is provided, including sample collection, filtering, sample processing, and is discussed with the context of several case studies.

Water Quantity and Hydrology

Freshwater ecosystems are naturally dynamic. The source of water, discharge, turnover, and residence times all affect which organisms can live in different freshwater habitats and are key determinants of freshwater ecosystem structure and function. Human-induced changes to the volume and timing of both surface and ground water flows are a leading driver of global declines in freshwater biodiversity and are likely to be exacerbated by climate change. The conservation of many wetlands around the world, including in some cases the preservation of unique flora and fauna, is now entirely dependent on continued human intervention and water management. Such management can only be successful if based on sound understanding of water budgets and hydrological processes informed by accurate hydrological monitoring. This chapter provides a brief introduction to hydrological monitoring—what needs to be measured and how—for freshwater ecology and conservation.

Diversity of Freshwater Ecosystems and Global Distributions

Freshwater ecosystems are found on all continents comprising many different types and sizes; and defined and classified in different ways. The hydrologic regime influences the many physical and chemical features of freshwater ecosystems and has temporal and dynamic dimensions for flowing (rivers—lotic systems) and standing waters (lakes and ponds—lentic systems) and others that may experience permanent flooding or large fluctuations in water depths. The water balance is commonly used to understand a system’s hydrology and provide insights into the key processes determining its functioning. Widely distributed, global mapping initiatives provide a general distribution of types, document latitudinal and longitudinal distribution, and provide a global coverage estimate of 12.5–14.4 × 106 km2. However, a comprehensive inventory and global map for these ecosystems still does not exist. Information on the specific features of rivers and streams, lakes and ponds, swamps and marshes, peatlands, and freshwater karst systems is provided.

Freshwater Ecosystem Security and Climate Change

In this chapter we review techniques that managers may use to respond to climate change. First, modelling the impacts of climate change on freshwater ecosystems is discussed. While hydro-climatic projections can be used their imprecision requires the selection of robust adaptation options that provide benefits under a range of possible climate outcomes. Second, contested concepts for managing freshwater ecosystems and resources are summarised, and we conclude that they may be used to develop and implement cross-sectoral policies that sustain freshwater ecosystems. Third, options for climate change adaptation for freshwater ecosystems recommends application of six principles, emphasising: accommodation of change; application of ecological and socio-economic targets across multiple scales; maintaining connectivity, conservation of refugia, and representative habitats; initial implementation of no- and low-regret adaptation interventions; agreeing on thresholds for ecological change that trigger new management interventions; and scientific monitoring and evaluation. We conclude by considering how to manage the negative impacts and seize positive synergies in climate change responses: conservation advocates must engage with agriculture, energy, and water resources sectors if freshwater ecosystems are to be incorporated in their decisions.

Freshwater Ecosystem Services and Functions

Freshwater ecosystems provide many ecosystem services for people who use them directly as well as indirectly both through using wetland products and through passive activities associated with the existence of the ecosystem. Despite these benefits being widely recognised through international processes and national or local analyses, many freshwater ecosystems are still being degraded or destroyed. In many cases, there is limited understanding of the basic ecological functions that support the services that benefit so many people. With these situations in mind an appraisal of how to measure ecosystem services and functions is provided, building on the approaches presented by the Ramsar Convention approximately a decade earlier, and accompanied by a review of open-access toolkits for measuring or evaluating ecosystem services. A river catchment in eastern Australia is used as an example to illustrate the type of changes that have occurred in freshwater ecosystem services.

Microorganisms 1

This chapter gives a broad overview of freshwater algae in standing (lentic) and flowing (lotic) waters, with information on their morphological and taxonomic diversity. Algal communities are considered in relation to phytoplankton, substrate-attached and biofilm organisms. Methods are given for their collection, sample processing, enumeration, and biomass estimation in different aquatic situations. The relevance of these algae to human activities is considered particularly in relation to eutrophication of standing waters and the occurrence of harmful algal blooms. Control strategies to limit the growth of colonial blue-green algae are discussed within the context of an integrated management policy