Lecture 1 Introduction to Freshwater
Page 1: Introduction to Freshwater Biology
Module Coordinator: Sarah Dalesman (sad31@aber.ac.uk)
Support: Dan Mills (dam134@aber.ac.uk)
Page 2: Course Structure
Course Format:
Lectures focused on temperate systems.
Practical sessions based on sampling freshwater environments and invertebrate identification.
Assessment Breakdown:
Coursework: Report on the identification of invertebrates and data collected in the field/laboratory (50%).
Exam: 2 essay questions (50%) with a choice of 4 from the lecture content.
Note: Practical information to be released in the upcoming weeks.
Page 3: The Global Water Cycle
Key Concepts:
Volumes and Residence Times:
Oceans: 1,370,000 km³ (t = 102 - 104 years)
Glaciers: 29,000 km³ (t = 16,000 years)
Lakes & Rivers: 230 km³ (t = 0.03 - 100 years)
Groundwater: 8400 km³ (t = 1 - 300 years)
Percentage distribution of water:
Oceans: 97.2%
Glaciers: 2.1%
Lakes & Rivers: 0.6%
Atmosphere: 0.001%
Fluxes: Precipitation, Evaporation, Run-off.
Page 4: Importance of Catchment in Freshwater Biology
Definitions and Processes:
Catchment: The area of land where water collects when it rains.
Hydrological Processes:
Evapotranspiration: Loss of water from the soil and plants.
Surface flow: Movement of water over land.
Infiltration: Water entering the soil.
Groundwater flow: Movement of water underground.
Page 5: River Systems Overview
Characteristics of River Systems:
Organized into natural units, biologically isolated.
Dendritic patterns indicate connectivity.
Features include estuaries, lakes within rivers, and interconnected systems.
Page 6: Stream Order and Distribution
Concept of Stream Order:
Classification based on the number of streams and mean length.
Observation that smaller streams are more common and shorter.
Page 7: Slope and Channel Gradient
Influence of Slope on River Systems:
Slope decreases with distance/order.
The shape of the slope curve can vary significantly.
Definitions: Slope = rise/distance (e.g., 1m/100m = 0.01 = 1%).
Page 8: Flow Dynamics in Streams
Factors Influencing Velocity:
Velocity (V) increases with slope, flow, and radius.
Affected by roughness or friction coefficient (Manning's n).
Higher values of n indicate greater roughness.
Page 9: Understanding Ponds and Lakes
Characteristics of Ponds vs. Lakes:
Pond: Shallow enough for light to reach the bottom, allowing for rooted plants.
Lake: Deep enough to form an aphotic zone, lacking rooted plants and characterized by various ecological zones.
Page 10: Dynamics of Lakes
Lakes as Dynamic Systems:
Lakes evolve over time, influenced by their size, shape, history, and environmental factors.
Can form stable stratification layers based on temperature and density.
Page 11: Biodiversity in Freshwater Systems
Freshwater Biological Diversity:
Generally less diverse than marine systems.
Phylogenetic Comparisons:
Freshwater: 37 Phyla
Marine: 58 Phyla (17 exclusive)
Page 12: Freshwater vs. Marine Phyla
Distribution of Major Groups:
Freshwater ecosystems host diverse groups such as Protozoa, while others are predominately marine.
Page 13: Fish Diversity Comparison
Diversity Ratios:
Freshwater fish: 1 species per 15 km³.
Marine fish: 1 species per million km³.
Freshwater constitutes a small percentage of Earth's water (0.02%).
Page 14: Investigating Freshwater Fish Diversity
Factors to Consider:
Examine academic literature for potential reasons why freshwater fish exhibit higher diversity compared to marine species.
Page 15: Evolutionary Origins of Freshwater Species
Colonization Patterns:
Primary colonization from marine environments followed by adaptations for freshwater.
Secondary colonization from land encounters.
Page 16: The Role of Prokaryotes
Key Function of Prokaryotes:
Essential for ecosystem functioning; include Archaea and Bacteria.
Page 17: Eukaryotic Diversity
Categories of Eukaryotes:
Fungi: Few aquatic representatives, important decomposers.
Plantae: Diverse group contributing to food webs (e.g., green algae, macrophytes).
Protista: Present in both freshwater and marine environments.
Page 18: Phyla of Marine Origin
Aquatic Invertebrates:
Introduces various groups like Porifera (sponges), Cnidaria (jellyfish), and more that have freshwater representatives.
Page 19: More Marine Origin Taxa: Parasites and Predators
Common Groups:
Flatworms (Platyhelminthes): Includes various parasitic forms.
Nematoda and other groups contribute to freshwater predator dynamics.
Page 20: Other Freshwater Fauna
Diversity within Rotifera and Annelida:
Highlights important roles of benthic and planktonic rotifers, roundworms, and segmented worms.
Page 21: Crustaceans and Their Roles
Crustacea in Freshwater:
Various groups including shrimp and copepods, crucial for aquatic food webs.
Page 22: Fish in Freshwater Ecosystems
Proportion of Fish Species:
Freshwater fish represent about 9% of identified species; includes various orders like ray-finned fish and lampreys.
Page 23: Mollusks in Freshwater Systems
Mollusca Overview:
Includes both freshwater and marine forms (e.g., pearl mussel).
Page 24: Terrestrial Phyla in Fresh Waters
Influences of Terrestrial Phyla:
Many life stages may occur out of water, reducing biological isolation effects.
Page 25: Insect Diversity in Freshwater
Insect Orders:
Highlights diverse orders such as Ephemeroptera (mayflies), Plecoptera (stoneflies), and Odonata (dragonflies).
Page 26: Holometabolous Insects
Key Insect Groups:
Includes Trichoptera (caddisflies) and Diptera (flies), showing diverse life histories.
Page 27: Arachnid Diversity
Freshwater Spiders:
Overview of a single British freshwater species, Argyroneta aquatica.
Page 28: Charismatic Freshwater Fauna
Diversity of Charismatic Species:
Roughly 3% of identified freshwater species are considered charismatic.
Page 29: Adaptive Evolution in Freshwater
Adaptive Strategies:
Life forms adapt due to diverse evolutionary origins. For further reading, refer to Balian et al., 2008 on freshwater biodiversity.