Until August 2004, Ystuvíkurstrýtur chimneys were the only confirmed hydrothermal chimneys in shallow waters in the world. Then a new site was found in Eyjafjörður by the geo-survey boat Baldur on a survey for Akureyri municipal water and power company and Iceland Geosurvey (Ísor).

This area is situated about 500 m north of the small peninsula Arnarnes (hence the name Arnarnesstrýtur) and 4 km sailing distance from the harbour of the small hamlet of Hjalteyri. This hydrothermally active zone stretches for about 500 m from 25 m to 50 m depth. A few days after the find a diver went down to confirm that these were hydrothermally active chimneys.

Arnarnesstrýtur are in some ways different from the previously known Ystuvíkurstrýtur close by. The main difference is that the hydrothermally active area is much larger or stretching about 500 m. It not only characterized by many chimneys of various sizes (as opposed to only 3 at Ystuvíkurstrýtur) but also venting fissures.

The Arnarnesstrýtur are also at a much shallower depth or from about 25 m to 40 m. The top of the chimneys are however at similar depths as in Ystuvíkurstrýtur and therefore the Arnarnesstrýtur are not as high from the bottom. This is probably due to wave action, it restricts how close to the surface the chimneys can reach. The area lies approximately in a straight line on a gently sloping plateau for or about 750 meters. It is difficult to estimate the age of the chimneys but there are indicators that they can grow quite rapidly (many cm per month).

The ecosystem in Arnarnesstrýtur seems more diverse than at Ystuvíkurstrýtur which can be because it is in shallower waters or because the multitude of chimneys provide a more diverse environment. Hydrozoans, bryozoans, sponges, sea anemones, blue mussels and red algae cover the bottom around the chimneys, the only bare areas are directly above the venting fluid. Small mobile invertebrates are also abundant there as well as fishes.

The fish species noted around the vent sites are Atlantic catfish and butterfish hiding in crevasses, male lumpsuckers apparently guarding their nest, and cod, saithe and haddock of various age classes (from 0-goup and up). All of these species are however common in the fjord. It is quite unclear if the vents provides some unique benefits for the fishes.

HV

Niurstöður úr botnmælingum Baldurs, séð inn fjörðinn, Laufásgrunn til vinstri, Arnarnesnafir og strýturnar til hægri (mynd Ísor) Niurstöður úr botnmælingum Baldurs, séð inn fjörðinn, Laufásgrunn til vinstri, Arnarnesnafir og strýturnar til hægri (mynd Ísor)

Vísindamaður frá NASA að prófa tækjabúnað við Arnarnesstrýturnar (mynd Erlendur Bogason)) Vísindamaður frá NASA að prófa tækjabúnað við Arnarnesstrýturnar (mynd Erlendur Bogason))

Nokkrar strýtur við Arnarnes (mynd Erlendur Bogason) Nokkrar strýtur við Arnarnes (mynd Erlendur Bogason)