ENVR101 Freshwater Biodiversity in Aotearoa

Grades were released before the tutors could double-check them, but they are being checked, and it should be resolved very soon.

Overfishing of keystone predators (koura, tamurai, snapper) leads to cascading effects.
Urchin (kinah) population bursts decimate kelp forests.
Marine reserves are effective for rehabilitation with community input.
New Zealand has 44 marine reserves, covering ~10% of coastlines.
Ocean surface temperature varies by 6 degrees from north to south.
Marine biodiversity has declined since human arrival.
MacDiarmid and Pinkerton (2015) found sharp declines in biomass with whaling and commercial fishing in the 1700s and widespread fishing in the 1950s.
Fiji imposes reproductive size limits for fish conservation.

Freshwater is rare, making up only 3% of the water on Earth.
Only one-third of freshwater is easily accessible to humans.
Conflicts over freshwater accessibility have increased, especially in the last decade due to climate change and drought.
The Colorado River example showcases water justice issues and creative solutions for water scarcity.

British scientist, wrote "Homage to Santa Rosalia or Why Are There So Many Kinds of Animals?"
Explored trophic complexity and niche partitioning.
Paradox of the Plankton addresses the high diversity of plankton that seemingly eat the same things and occupy the same niche space.
Observed species dominance changes throughout the year, suggesting no single equilibrium point.
Non-equilibrium and change is fundamental to the maintenance of diversity of these systems.

High diversity, including braided rivers, peat lakes, dune lakes, spring-fed streams, and wetlands.
Wetlands act like the kidneys of the earth, cleaning water and providing flood relief.
Urban development and agriculture threaten wetland systems.

Littoral zone: where land meets water, high biodiversity, shallow, and nutrient-rich.
Lymnetic zone: open water, divided into light zones (euphotic with light penetration, profundal without light) and temperature zones (epilimnion: warm water sits above, hypolimnion: cooler water sits on the bottom, thermocline).
The width and your depth of your littoral zone depends on the age of your freshwater system as well.

Native frogs: Critically endangered due to introduced predators, disease (fungus), and habitat loss.
High number of endemic freshwater birds (30% of native birds), including wetland birds and others adapted to specific habitats.
High diversity of freshwater fish, dominated by galaxiids (cool water trout-like species).
Allopatric speciation caused by tectonic activity and volcanoes, leading to isolated galaxiid populations.
Galaxiids are threatened by invasive species, habitat loss, and altered water flow.

Longfin eel (Anguilla dieffenbachii) is endemic; shortfin eel (Anguilla australis) also found in Australia and Pacific Islands.
Eels start as larvae, become glass eels, and then juveniles before maturing in freshwater systems for 25-80 years.
Adult eels migrate to the Pacific Ocean to breed, then die (semelparous).
Threats include overfishing, hydroelectric dams, stream barriers, and sewage discharge.
Climate change impacts: unpredictable rainfall, altered ocean currents, increased sedimentation, and off-season cyclones.

Many taonga species are at risk, including kakahi and longfin tuna.
Migratory fish populations have declined significantly since 1970.
Freshwater ecosystems are degrading rapidly.
Groundwater resources supply nearly half of the world's drinking water, but some are unsafe due to E. coli contamination.
Mahingakai (food gathering) is a cultural indicator of freshwater health and is threatened by declining water quality.
E. coli was sampled from watercress and in cockles at concentrations that exceeded health guidelines for human consumption.