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Posts Tagged aquatic ecology

Phreatogammarus fragilis: The fragile well shrimp Waiology Dec 06

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By Daniel Collins

Phreatogammarus fragilis is an endemic New Zealand crustacean that lives in aquifers. It is an amphipod (a relative of the sand hopper), and is one of the largest (commonly up to 25 mm excl. antennae) and strongest swimming of NZ’s stygofaunal* crustaceans. Because it is so rarely observed, it does not have a common name; the best translations are ‘fragile well shrimp’ or ‘fragile groundwater lobster’, ‘fragile’ probably because its appendages broke off when early specimens were being identified and preserved.

The individual below is a 12 mm-long female with a brood pouch beneath the abdomen. It is white and translucent because there is no point in investing in pigments if it’s too dark to see or if there’s no risk of sunburn. This individual was caught in a trap in a 6 m-deep well beside the Selwyn River in Canterbury by Nelson Bousted and identified by Graham Fenwick. It was photographed live in water in a custom-built aquarium with several off-camera flashes.

Photo credit: Nelson Boustead

Waiology will have some more in-depth science of stygofauna in a future post.

* Stygofauna: animals that live in groundwaters, named after the river in Greek mythology, the Styx, which separated the Earth from the Underworld.


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.

Map: Projected effects of climate change on New Zealand freshwaters Waiology Nov 27

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By Daniel Collins

Maps are helpful tools in communicating and understanding the potential implications of climate change. We have national maps of projected changes in temperature that show faster warming in the north, and in precipitation that show more rain in the south and west and less in the north and east. We also have national maps of projected changes in drought, that show much of the country is likely to experience more severe droughts.

Now, I am able to give you a map of the potential freshwater changes across New Zealand. This includes changes in snow, ice, river flow, groundwater, aquatic ecology, geomorphology, and water use/management.

This is an important step in synthesising and understanding climate change impacts, drawn from existing case studies across the country. Projections are pin-pointed on the map below; in some cases they are more national in scope (e.g., salinisation of coastal groundwater).

This illustrates quite a complex picture. Retreating snow and ice. More flow in Alps-fed rivers, less flow in others. Higher lake levels and lower lake levels. More water demand from both agriculture and city. Higher erosion as well as channel aggradation. Higher lake nutrient levels and more frequent algal blooms.

There is a lot we know but also a lot we don’t know. As yet, we cannot provide a complete national assessment for river flows, nor for groundwater recharge. And very little research has connected the dots between climate change and aquatic ecology. But as new studies are carried out this map will be expanded and the gaps filled in.

In the near future I will describe the projected changes in more detail, so stay tuned.


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.

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