Editing Porpoise (section)

====Environmental hazards====
{{See also|Marine mammals and sonar}}
Porpoises are very sensitive to [[anthropogenic effect|anthropogenic]] disturbances,<ref name=":0">{{cite journal |title=Harbour porpoises (''Phocoena phocoena'') stranded along the southern North Sea: an assessment through metallic contamination |last1=Mahfouz |first1=C |last2=Henry |first2=F |last3=Courcot |first3=L |last4=Pezeril |first4=S |last5=Bouveroux |first5=T |last6=Dabin |first6=W |last7=Jauniaux |first7=T |last8=Khalaf |first8=G |last9=Amara |first9=R |year=2014 |journal= Environmental Research|doi=10.1016/j.envres.2014.06.006 |pmid=24981825 |volume=133 |pages=266–73|bibcode=2014ER....133..266M |hdl=2268/169176 |url=http://orbi.ulg.ac.be/handle/2268/169176 |hdl-access=free }}</ref> and are [[keystone species]], which can indicate the overall health of the marine environment.<ref name=":0" /> Populations of harbor porpoises in the North and Baltic Seas are under increasing pressure from anthropogenic causes such as offshore construction, ship traffic, fishing, and military exercises.<ref>{{cite journal |last1=Siebert |first1=Ursula |last2=Pozniak |first2=Blazej |last3=Hansen |first3=Kirstin |last4=Anderson |last5=Nordstrom |first5=Gwyneth |last6=Teilmann |first6=Jonas |last7=Van Elk |first7=Niels |last8=Vossen |first8=Ardnt |last9=Dietz |first9=Rune |year=2011 |title=Investigations of Thyroid and Stress Hormones in Free-Ranging and Captive Harbor Porpoises (''Phocoena phocoena''): A Pilot Study |journal=Aquatic Mammals |volume=37 |issue=4 |pages=443–453 |doi=10.1578/am.37.4.2011.443}}</ref> Increasing pollution is a serious problem for marine mammals. Heavy metals and [[plastic pollution|plastic waste]] are not biodegradable, and sometimes cetaceans consume these hazardous materials, mistaking them for food items. As a result, the animals are more susceptible to diseases and have fewer offspring.<ref name=wdcs>{{cite book |author=Cara E. Miller |title=Current State of Knowledge of Cetacean Threats, Diversity, and Habitats in the Pacific Islands Region |publisher=Whale and Dolphin Conservation Society |year=2007 |access-date=5 September 2015 |isbn=978-0-646-47224-9 |url=http://uk.whales.org/sites/default/files/whales-and-dolphins-in-the-pacific-islands.pdf |archive-url=https://web.archive.org/web/20150908003502/http://uk.whales.org/sites/default/files/whales-and-dolphins-in-the-pacific-islands.pdf |archive-date=8 September 2015  }}</ref> Harbour porpoises from the [[English Channel]] were found to have accumulated heavy metals.<ref name=":0" />

The military and geologists employ strong [[sonar]] and produce an increases in noise in the oceans. [[Marine mammal]]s that make use of [[biosonar]] for orientation and communication are not only hindered by the extra noise, but may race to the surface in panic. This may lead to a bubbling out of blood gases, and the animal then dies because the blood vessels become blocked, so-called [[decompression sickness]].<ref>{{cite book |author1=M. Andre |author2=T. Johansson |author3=E. Delory |author4=M. van der Schaar |title=Europe Oceans 2005 |chapter=Cetacean biosonar and noise pollution |publisher=Oceans 2005–Europe |year=2005 |volume=2 |pages=1028–1032 Vol. 2 |doi=10.1109/OCEANSE.2005.1513199 |isbn=978-0-7803-9103-1 |s2cid=31676969 }}</ref> This effect, of course, only occurs in porpoises that dive to great depths, such as Dall's porpoise.<ref>{{cite journal |author=Kastelein, R. A. |author2=Schop, J. |author3=Gransier, R. |author4=Steen, N. |author5=Jennings, N. |title=Effect of Series of 1 to 2 kHz and 6 to 7 kHz Up-Sweeps and Down-Sweeps on the Behavior of a Harbor Porpoise (''Phocoena phocoena'') |doi=10.1578/AM.40.3.2014.232 | volume=40 |issue=3 |journal=Aquatic Mammals |pages=232–242|year=2014 }}</ref>

Additionally, civilian vessels produce sonar waves to measure the depth of the body of water in which they are. Similar to the navy, some boats produce waves that attract porpoises, while others may repel them. The problem with the waves that attract is that the animal may be injured or even killed by being hit by the vessel or its propeller.<ref>{{cite journal |last1=Culik |first1=B. |last2=von Dorrien |first2=C. |last3=Muller |first3=V. |last4=Conrad |first4=M. |year=2015 |title=Bioacoustics |journal=The International Journal of Animal Sound and Its Recording |volume=24 |issue=3 |issn=0952-4622}}</ref>