The Oceans Surrounding Sanibel Island, Florida, USA
- The Persaud Catalog
- Oct 20
- 7 min read
In today's article, we will discuss the oceans surrounding Sanibel Island, an island on the Gulf Coast of southern Florida.
The island is most well known for its sandy beaches, shells, & wildlife reserves. The primary wildlife reserve on the island is J.N. “Ding” Darling National Wildlife Refuge. The scenery of the island is superb, & adds beautifully to the hiking paths of the island.
The island is extremely close to the mainland, being only 1.75 nautical miles (2.013864 miles or 3.241 kilometers) away at its closest point. The western coast of the island is well known to contain whelks, bivalves, sand dollars, & scallops, which attract many tourists as well as recreational fishermen.
Many seashell enthusiasts also enjoy the island for this reason, & can be seen gathering or admiring shells on the early mornings. Additionally, these seashell enthusiasts have an entire museum to look into, as Sanibel Island has a museum dedicated to the study of seashells, conchology, & malacology. This museum is known as the Bailey-Matthews National Shell Museum.
Off the coast of the island, divers & fishermen alike have something else to look forward to. In the oceans, there are a variety of different marine organisms, ranging from dolphins to amberjacks.
The island is in the Atlantic Ocean, in the Gulf of Mexico. This makes it a prime area for turtles to migrate to, & lay eggs. On the island, eggs from the following turtle species may be seen: Chelonia Mydas, (Green Turtle), Caretta Caretta (Loggerhead Turtle), Lepidochelys Kempii (Kemp’s Ridley Sea Turtle), Demorchelys Coriacea (Leatherback Turtle), & Eretmochelys Imbricata (Hawksbill Turtle).
In this article, we will discuss the salinity, tides, temperatures, marine geography, & depth of the oceans surrounding Sanibel Island, the most prominent marine ecosystems of the oceans surrounding Sanibel Island, & the documented marine flora & fauna of the oceans surrounding Sanibel Island,, let us delve into the oceans surrounding Sanibel Island!
The Salinity, Tides, Temperatures, Marine Geography, & Depth Of The Oceans Surrounding Sanibel Island
Unfortunately, the salinity around Sanibel Island has yet to be measured. The salinity levels of the Atlantic Ocean at any given time are between 35.5 & 34.5 parts per thousand, so it can be assumed that the Salinity around Sanibel Island falls in between that. Salinity is measured in 1,000-gram increments. For every 1000 grams of water, there will be a certain number of grams that are pure salt. This is how salinity or saline level is measured. There are also no ongoing factors that would lead to the salinity level being altered.
The tidal charts for the island can be found on a variety of websites, a few of which are: https://tides4fishing.com, https://www.tideschart.com, https://www.tidetime.org, https://www.seatemperatu.re. It seems that the tides around the island rarely get over 5.53 feet (1.685544 meters).
The temperature charts can be found on similar websites, including: https://seatemperature.net, https://seatemperature.info, https://www.seatemperatu.re, https://www.watertemp.org, https://www.seatemperature.org, & https://tides4fishing.com. Currently, the average yearly water temperature is 76.533333333333° Fahrenheit (24.7407407407405344° Celsius), with the hottest month being August. In this temperature, a full-body wetsuit with 3 millimeters of thickness is recommended for swimming, or any oceanic activities.
The water around the area is not very polluted, & is completely safe for swimming. On practically every day of summer swimmers, wind skiers, & surfers can be seen enjoying the beaches. There are occasional rip currents near beaches, though they rarely endanger swimmers.
The deepest oceanic point within 5 Nautical Miles of Sanibel Island is 34.8 feet (10.60704 meters) deep. The ocean floor around the island is primarily comprised of mud, sand, rock, & shell. Due to the island being close to the mainland, there are very few seamounts near it.
A few of the most popular beaches on the island are deemed to be as follows: Bormann’s Beach, Blind Pass Beach, Lighthouse Beach Park, Silver Key Beach, Algiers Beach, & finally Tarpon Bay Beach.
The Most Prominent Marine Ecosystems Of The Oceans Surrounding Sanibel Island
Ecosystem Type No. 1: Coastal Mangrove Forests
Along the coasts of the island, Coastal Mangrove forests can be found. Coastal mangrove forests are a particular kind of forest, that adorn the shoreline of the island.
These forests are incredibly important to biodiversity, for terrestrial, oceanic, & avian creatures. The forest provides shelter, food, & a spawning ground for many different species. The primary species of mangrove tree on the island are: Rhizophora Mangle (Red Mangrove), Avicennia Germinans (Black Mangrove), & Laguncularia Racemosa (White Mangrove).
The largest areas of mangrove trees are found on the eastern side of the island, however, smaller parts are also found on the western side. In addition to being useful for the creatures, the mangroves shield the island from storms, & decrease the effects of shoreline erosion.
For this reason, there is an Adopt a Mangrove program organized by the Sanibel-Captiva Conservation Foundation. By adopting a mangrove, one will contribute to the safety & biodiversity of Sanibel Island. The link to this program is as follows: https://sccf.org/adoptamangrove/.
Ecosystem Type No. 2: Rocky Reefs
Rocky Reefs are some of the most common oceanic ecosystems near Sanibel Island. These oceanic ecosystems are similar in composition to Coral Reefs, except for the fact that they are made of rock. Generally, they are large rocky outcroppings on the ocean floor. These rocky reefs are often covered in bivalves, due to the fact that bivalves tend to prefer rocky bottomed areas as opposed to sand bottomed areas. Anemones are also commonly seen. Rock Reefs are also safe havens for juvenile fish, as well as juvenile octopi.
These rocky reefs tend to be further out to sea, & not appear immediately along the coastline.
The Documented Marine Flora Of Sanibel Island
Unfortunately, we have very little information on the seagrasses, & algae of the island. For the purposes of this section, we will be focusing on the mangrove trees of the island. Below, we will go through each of the mangrove tree species found on the island. Each species will be getting its own subsection. With this being said, let us begin with Rhizophora Mangle (Red Mangrove).
Mangrove Type. No. 1: Rhizophora Mangle (Red Mangrove)
Rhizophora Mangle is a species of mangrove native to Florida. This species can grow to a maximum of 50 feet (15.24 meters) tall, & 40 feet (12.192 meters) wide. The bark of the tree is reddish brown in colour, though it becomes grey with age. The tree also produces small white flowers. When fully grown, it is an incredibly useful means of erosion control. The tree is incredibly saline-resistant, surviving up to 90 parts per thousand salinity. Once the tree dies, its branches will provide a home for microorganisms, which will then bring nutrients into the ecosystem.
Mangrove Type No. 2: Avicennia Germinans (Black Mangrove)
Avicennia Germinans is a species of Mangrove native to the southeastern coastal regions of the United States. This species can grow to a maximum of 40 feet (12.192 meters) tall, & 30 feet (9.144 meters) wide. This species is known for its long white flowers, silver leaves, & dark bark. They have a very high salinity tolerance, as Florida’s mangroves often flood.
Mangrove Type No. 3: Laguncularia Racemosa (White Mangrove)
Laguncularia Racemosa is a species of Mangrove native to Florida. They are known to grow to a maximum of 40 feet (12.192 meters) tall, & 30 feet (9.144 meters) wide. The base of the mangrove is white, however, it gets darker as further up the trunk. Their leaves are leathery, & rounded. This species is extremely saline-tolerant, & is able to survive in many different salinity levels.
The Documented Marine Fauna Of Sanibel Island
The marine fauna of Sanibel Island is incredibly diverse. With the water staying warm, marine mammals will often migrate here in the winter. Additionally, many species will migrate to the island, & then go back out into the gulf, or simply breed here. For this reason, tracking the population of oceanic creatures is extremely difficult.
As of 2025, no marine creatures have been discovered that are endemic to the island.
A list of the majority of marine species on the island can be found at https://www.inaturalist.org.
Directories / Credits
Citation No. 1: “Wetsuit thickness & temperature guide”, Written by Mark Evans, & Published on April 24th, 2023, at 3:05 PM. Published By Scuba Divers Magazine. Retrieval Date: January 18th, 2024.
Citation No. 2: “Top 9 Beautiful Beaches On Sanibel & Captiva Island (2022)”, Written By Unclear, & Published in 2022. Published by the Sanibel Captiva Island Guide. Retrieval Date: January 19th, 2024.
Citation No. 3: “9 Best Beaches On Sanibel Captiva Island”, Written By Unknown, & Published at an Unknown Date. Published by Hotels.com. Retrieval Date: January 19th, 2024.
Citation No. 4: “About Mangroves”, Written By Unknown & Published at an Unknown Date. Published by The City Of Sanibel. Retrieval Date: January 19th, 2024.
Citation No. 5: “Rhizophora Mangle (Red Mangrove)”, Written By Unknown & Published at an Unknown Date. Published by Gardenia. Retrieval Date: January 19th, 2024.
Citation No. 6: “Rhizophora Mangle” Written By Unknown & Published at an Unknown Date. Published by the Animal Diversity Web. Retrieval Date: January 19th, 2024.
Citation No. 7: “Avicennia Germinans (Black Mangrove)” Written By Unknown & Published at an Unknown Date. Published by Gardenia. Retrieval Date: January 19th, 2024.
Citation No. 8: “Black mangrove,
Avicennia germinans, Avicenniacea” Written by Unknown & Published at an Unknown Date. Published by The Institute for Regional Conservation. Retrieval Date: January 19th, 2024.
Citation No. 9: “Laguncularia Racemosa (White Mangrove)”, Written By Unknown & Published at an Unknown Date. Published by Gardenia. Retrieval Date: January 19th, 2024.
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