Editing Hudson River (section)

==Flora and fauna==
{{See also|Marine life of New York–New Jersey Harbor Estuary}}

===Plankton===
[[File:Bird on the bank of the Hudson River 1.jpg|thumb|A juvenile [[house sparrow]] by the Hudson River]] [[Zooplankton]] are abundant throughout both fresh and saltwater portions of the river, and provide a crucial food source for larval and juvenile fish.<ref name="RP"/>

===Invertebrates===
The [[benthic zone]] has species capable of living in soft bottom habitats. Within freshwater regions, there are animal species including larvae of [[chironomid]] flies, [[oligochaete]] worms, predatory fly larvae, and [[amphipod]]s. In saline regions, there are abundant [[polychaete]] [[annelid]]s, amphipods, and some mollusks such as clams. These species burrow in the sediment and accelerate the breakdown of organic matter. [[Atlantic blue crab]]s are among the larger invertebrates, at the northern limit of their range.<ref name="RP"/>

The entire Hudson was once far more populated with native suspension-feeding [[bivalves]]. Freshwater mussels were common in the river's [[limnetic zone]], but populations have been decreasing for decades, probably from altered habitats and the invasive zebra mussel. Oyster beds were once pervasive in the saltwater portion, but are now reduced through pollution and exploitation.<ref name="RP"/>

===Fish===
About 220 species of fish, including 173 native species, currently are found in the Hudson River.<ref name="Species">{{cite news|last=Lake|first=Tom|title=Hudson River Watershed Fish Fauna Check List |publisher=NYSDEC Hudson River Estuary Program|url=http://www.dec.ny.gov/docs/remediation_hudson_pdf/hrepfishlist.pdf|date=October 20, 2016|access-date=September 26, 2017|archive-url=https://web.archive.org/web/20170320225017/http://www.dec.ny.gov/docs/remediation_hudson_pdf/hrepfishlist.pdf|archive-date=March 20, 2017|url-status=live}}</ref> Commercial fishing was once prominent in the river, although most were shut down in 1976 due to pollution; few survive today. [[American shad]] are the only finfish harvested for profit, though in limited numbers.<ref name="RP"/>

Species include [[striped bass]], the most important game fish in the Hudson. Estimates of the striped bass population in the Hudson range to nearly 100&nbsp;million fish.<ref name="Million1"/><ref name="Million2"/> [[American eel]]s also live in the river before reaching breeding age; for much of this stage they are known as [[glass eel]]s because of the transparency of their bodies. The fish are the only [[catadromous]] species in the Hudson's estuary.<ref name="HRPark"/>

The [[Atlantic tomcod]] is a unique species that adapted resistance to the toxic effects of the PCBs polluting the river. Scientists identified the genetic mutation that conferred the resistance, and found that the mutated form was present in 99 percent of the tomcods in the river, compared to fewer than 10 percent of the tomcods from other waters.<ref name="HRPark"/><ref name="Welsh"/> The [[hogchoker]] [[flatfish]] have been historically abundant in the river, where farmers would use them for inexpensive livestock feed, giving the fish its name.<ref name="HRPark" /> Other unusual fish found in the river include the [[northern pipefish]], the [[lined seahorse]], and the [[northern puffer]].<ref name="HRPark"/>

The [[Atlantic sturgeon]], a species about 120&nbsp;million years old, enter the estuary during their annual migrations. The fish grow to a considerable size, up to {{convert|15|ft}} and {{convert|800|lbs}}.<ref name="HRPark"/> The fish are the symbol of the Hudson River Estuary. Their smoked flesh was commonly eaten in the river valley since 1779, and it was sometimes known as "Albany beef". The city of Albany was called "Sturgeondom" or "Sturgeontown" in the 1850s and 1860s, with its residents known as "Sturgeonites". The "Sturgeondom" name lost popularity around 1900.<ref name="AlbanyBeef"/> The fish have been off limits from fishing since 1998. The river's population of [[shortnose sturgeon]] have quadrupled since the 1970s, and are also off limits to all fishing as they are a federally endangered species.<ref name="RP"/>

Lined seahorse or northern seahorse (''[[Hippocampus erectus]]'') are found in the brackish waters of the Lower [[New York Bay]], [[New York Harbor]] and surrounding waters (including [[Raritan Bay]] and [[Sandy Hook Bay]]) and the Hudson River [[estuary]].<ref>{{Cite web |date=2016-07-20 |title=Spot a Seahorse in NYC |url=https://slownaturefastcity.com/2016/07/20/spot-a-seahorse-in-nyc/ |access-date=2022-04-19 |website=Slow Nature Fast City |language=en}}</ref><ref>{{Cite web |last=Pereira |first=Sydney |date=2021-04-18 |title=Seahorse Spotted In The Hudson River, Marking Yet Another Hopeful Sign Of Spring |url=https://gothamist.com/ |access-date=2022-04-19 |website=Gothamist |language=en}}</ref><ref>{{Cite web |title=Seahorses Really Do Swim in NY Harbor |url=http://www.nyharbornature.com/1/post/2016/07/-seahorses-really-do-swim-in-ny-harbor.html |access-date=2022-04-19 |website=NY HARBOR NATURE |language=en }}{{Dead link|date=December 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{Cite web |date=2012-10-04 |title=There are seahorses living in New York City |url=https://grist.org/article/there-are-seahorses-living-in-new-york-city/ |access-date=2022-04-19 |website=Grist |language=en-us}}</ref><ref>{{Cite web |last=Gonzalez • • |first=Georgina |title=The Many Creatures of the Hudson River May Surprise You |url=https://www.nbcnewyork.com/news/local/the-many-creatures-of-the-hudson-river-may-surprise-you/3003201/ |access-date=2022-04-19 |website=NBC New York |date=April 16, 2021 |language=en-US}}</ref>

===Marine and invasive species===
[[Marine life]] is known to exist in the estuary, with seals, crabs, and some whales reported. On March 29, 1647, a white whale swam up the river to the [[Rensselaerswyck]] (near Albany). [[Herman Melville]], author of ''[[Moby-Dick]]'', lived in and near Albany from 1830 to 1847, and was known to have ancestry from [[New Netherland]], leading some to believe stories of the whale sighting inspired his novel.<ref name="Whale1"/>

Non-native species often originate in New York Harbor, a center of long-distance commerce. Over 100 foreign species reside in the river and its banks. Many of these have had significant effects on the ecosystem and natural habitats. The [[water chestnut]] produces a vegetative mat that reduces oxygen content in the water below, enhances sedimentation, impedes small vessel navigation, and is a hazard to swimmers and walkers. The zebra mussel arrived in the Hudson in 1989 and has spread through the river's freshwater region, reducing photoplankton and river oxygen levels. Positively, the mussel clears suspended particles, allowing for more light to aquatic vegetation. In saltwater areas, the [[green crab]] spread in the early 20th century and the [[Japanese shore crab]] has become dominant in recent years.<ref name="RP"/>

===Habitats===
The Hudson has a diverse array of habitat types. Most of the river consists of deep water habitats, though its tidal wetlands of freshwater and salt marshes are among the most ecologically important. There is strong biological diversity, including intertidal vegetation like freshwater [[cattail]]s and saltwater [[cordgrass]]es. Shallow coves and bays are often covered with submarine vegetation; shallower areas harbor diverse [[benthic]] fauna. Abundance of food varies over location and time, stemming from seasonal flows of nutrients. The Hudson's large volume of suspended sediments reduces light penetration in the area's water column, which reduces photoplankton photosynthesis and prevents sub-aquatic vegetation from growing beyond shallow depths. The oxygen-producing phytoplankton have also been inhibited by the relatively recent invasion of the [[zebra mussel]] species.<ref name="RP"/>

The Hudson River estuary is the site of wetlands from New York City all the way up to Troy. It has one of the largest concentrations of freshwater wetlands in the Northeast. Even though the river can be considered brackish further south, 80 percent of the wetlands are outside the influence of the saltwater coming from the Atlantic Ocean. Currently, the river has about {{convert|7000|acres|km2}} acres of wetlands, and rising sea levels due to [[climate change]] are expected to lead to an expansion of that area. Wetlands are expected to migrate upland as sea level (and thus the level of the river) rises. This is different from the rest of the world, where rising sea levels usually leads to a reduction in wetland areas. The expansion of the wetlands are expected to provide more habitat to the fish and birds of the region.<ref name="wetlands expansion"/>