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Marvellous mangroves!

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As divers, I’m guessing most of us love diving on coral reefs; if those reefs are pristine and full of life, even better! Coral reefs are incredible and diverse ecosystems, but they are strongly linked and interdependent on three other ecosystems: seagrasses, mangroves and rivers. Here I’m going to discuss mangroves, and why they are one of the most important ecosystems to conserve in order to have beautiful, healthy coral reefs. Hopefully I can convince every diver to love them as much as I do and to explore our options in protecting these habitats. Though historically, mangroves were viewed as insect filled, tangled and muddy swamps and shrub forests, we have become increasingly aware of how diverse and special this amazing habitat is for both wildlife and protecting our shorelines from extreme weather events.

So, what is a mangrove?

Mangroves are trees and shrubs that love very warm, wet conditions and grow in saline coastal habitats in tropics and subtropics. You have probably seen them fringing islands and coastlines when diving on coral reefs. They can often be recognised by their dense tangle of prop root that make the trees look like they are on stilts. Mangroves are unique because they can live in areas with low oxygen soil and where the water has a variable salt content. As they live in the coastal intertidal zone, the roots can cope with being flooded twice a day. They are flowering plants, where the upper trunk, branches and leaves live above the water line and the lower trunk and roots can live below.

There are over 80 different species of mangrove tree and several more species associated with mangroves for their ability to tolerate the coastal intertidal zone, such as buttonwoods. The Asia-Pacific region has the most diversity and the largest mangrove region in the world is The Great Sundarbans in Bangladesh (a UNESCO World Heritage Site). Having said this, there are three main dominant types of mangroves in a mangrove forest; red, black and white.

Red mangroves are evergreen trees that can grow to 25m, often less. They live closest to the water and elaborate arching prop roots and red bark colour make it very easy to identify. They are salt excluders; the roots contain a waxy substance that helps keep the salt out. If any salt does get through, it is deposited in older leaves and the tree sheds them. They produce propagules (seeds) that grow from the tree, then detach and stick into the mud or float away somewhere new.

Black mangroves live between red and white mangroves. The easily identifiable roots (pneumatophores) stick up vertically from sediment and are specially designed to take in oxygen, acting like snorkels in the water. Black mangroves have longer pointed leaves which are often covered in salt crystals and dark scaly bark. They produce seeds which germinate while still connected to the parent tree, so trees are often grouped together.

White mangroves live closest to the land in the back portion of the mangrove swamps, where they are unaffected by tidal inundation, except on spring tides. With no visible aerial roots, they may seem harder to identify, but the leaves have two glands at the base which excrete the salt taken in by the roots, so the leaves are often coated with white salt crystals. The salt crystals give this species its common name and the bark is lighter in colour.

Why should we love them?

Mangroves are ecosystem engineers, meaning they form their own ecosystem and provide habitats for other species, but they also have lots of benefits to us:

  1. Trapping sediments

Mangrove forests have huge root systems that slow the movement of tidal waters, making the sediment settle out of the water, the roots then trap this soft sediment and build up the muddy bottom. In dense forests, mangroves have created entire islands.

  1. Reducing wave action

The network of sediment-trapping roots stabilize the coastline, reducing erosion from wave and tidal action and providing a buffer, an important defence for costal ecosystems and communities from tropical storms and their storm surges.

  1. Important nursery grounds

Mangroves provide an intricate network of nursery habitat for many fish and invertebrate species, which move out to coral reefs and other ecosystems when they mature. The mangroves provide a safe haven for juvenile fish, including commercially important fisheries species, which seek food and shelter from predators. Many shark species, including lemon sharks, bull sharks and blacktip sharks, spend their juvenile years in mangrove forests.

  1. Rich biodiverse ecosystems

In addition to being a great habitat for the young of reef and pelagic species, mangroves are a primary habitat for mature individuals of many species of marine animal, amphibians, reptiles, seabirds and waterfowl. Mangroves are always teeming with life!

For anyone who enjoys diving on coral reefs, it is important to be aware that coral reefs and mangroves have a symbiotic relationship – the reefs protect the coast from being eroded by the sea, blocking the power of the open ocean and the mangroves trap the sediment washed from the land that would smother and kill the reef. Species depend on both ecosystems for different life stages and both ecosystems provide coastal protection and commercial value through fish stocks and tourism for us. Mangroves are one of the most valuable ecosystems in the world.

Threats

Unfortunately, like coral reefs, mangrove forests are under threat and are being lost at a very rapid rate. Clear cutting for aquaculture, mainly shrimp farming and coastal developments, such as marinas, housing and hotels is a major issue, as is harvesting for wood.

It is estimated that at least one third of all mangrove forests have been lost in the last few decades. Without protection, they may disappear in areas that cannot afford the ecological or economic loss. This in turn negatively effects our beloved coral reefs, which are already struggling with pollution, sedimentation, climate change, ocean acidification, overfishing and destructive commercial practices. After that thoroughly depressing paragraph, lets move onto the positive bit…

What can we do to help?

  1. Help support and encourage more protected areas. If you are travelling in an area with a protected area, donate or take a guided tour from rangers.
  2. Make sustainable choices; shrimp farming is a leading cause of mangrove habitat loss, know where your food is coming from and whether you should be making that choice. If you don’t want to give up a food, there is usually a sustainable option – it may cost a little extra, but it will be completely worth it!
  3. Spread the word! As ever, education is always important and particularly in countries with mangrove forests; many NGO’s work in schools to educate the next generation, which we can support through donations. However it isn’t just about spreading the word in other countries, the more people everywhere learn about the value of mangrove forests, the more drive there will be to protect this amazing habitat!

Visiting the mangroves

So, if you are now totally hooked on marvellous mangroves and want to go and see the wildlife for yourself, there are now many places that will take you snorkelling or on kayak tours. By picking an organisation that donates to mangrove protection or does educational programmes you get to help out while having a great time!

For more from CJ and Mike please click here.

CJ and Mike are dive instructors who have travelled all over the world pursuing their passion for the underwater world. CJ is a PADI MI and DSAT Trimix instructor with a degree in Conservation biology and ecology, who has been diving for 15 years. She loves looking for critters and pointing them out for Mike to photograph. Mike is a PADI MSDT who got back into diving in 2010. He enjoys practicing underwater photography and exploring new and exciting dive locales, occasionally with more than one tank. Follow more of their diving adventures at www.bimbleintheblue.com.

Marine Life & Conservation

White Shark Interest Group Podcast #007 – with ROB LAWRENCE

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Seventh in an exciting podcast series from Ricardo Lacombe of the White Shark Interest Group.

Episode 7 of the White Shark Interest Group Podcast, Facebook’s’ largest White Shark specific group, covering science, conservation, news, photography, video and debate.

This episode features Ricardo and Dirk speaking with the White Shark pioneer Rob Lawrence – the man who practically put False Bay, South Africa on the map for White Shark breaching behaviour.

If you have ever seen an image from South Africa of a white shark breaching from the water, be it on Airjaws, Nat Geo, BBC, Shark Week, or any photographs online and in books, you have Rob Lawrence to thank. He has worked behind the scenes with all those film crews and photographers to get them to where those sharks are, on a regular basis.

With his highly successful company African Shark Eco-Charters he has worked with hundreds of thousands of people to visit and dive with Great Whites and see the natural predation behaviour that False Bay is famous for. He has, without a doubt, been to Seal Island, False Bay, more than ANY other human being alive! He is here to share his experiences and knowledge – including the much talked about topic of where the White Sharks may have gone in the last couple of years.

This is a MUST LISTEN podcast and a rare chance to spend an hour in the company of a true pioneer and advocate in the shark world.

Click the links below to listen to the podcast series on the following audio channels:


Join the group: www.facebook.com/groups/whitesharkinterestgroup/

Instagram: www.instagram.com/whiteshark_interestgroup/

Website: www.whitesharkinterestgroup.com

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Dive Training Blogs

Reef Rescue Network launches new interactive map

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The Reef Rescue Network (RRN) was established in 2017 by the Perry Institute for Marine Science (PIMS) as a network of non-profit organizations and for-profit businesses committed to improving the condition of coral reefs by restoring populations of corals and other species that will build coral reef resilience. Since then the RRN has grown to include nearly 30 coral restoration sites in partnership with 25 local partners from 9 islands within The Bahamas as well as Aruba and St. Lucia. Through this partnership between coral reef scientist’s local conservation and education organizations and private businesses in the dive industry, the RRN is making significant advances in restoring coral and building reef resilience.

Visitors and locals can now immerse themselves in coral restoration activities at a partner location within the Reef Rescue Network. The network has coral nurseries that offer coral restoration experiences throughout The Bahamas, Aruba & St. Lucia. PIMS has developed a PADI Reef Rescue Diver Specialty Course that dive shops throughout the Reef Rescue Network are teaching. To participate, you must be a certified open water diver and at least 12 years old. The course takes one day and consists of knowledge development and two open water dives at a coral nursery.

You can learn how to assist with maintaining the nursery and get a hands-on experience or you can just scuba or snorkel the coral nursery as a fun dive to just observe and enjoy the nursery and marine life that it attracts. Another option is to scuba or snorkel one of the many restoration sites to view the corals that have been outplanted and witness for yourselves this habitat restoration and the marine life it has welcomed.

To find out more about the Reef Rescue Network, watch this video:

To visit the new Reef Rescue Network Interactive Map click here.

To learn more about the Reef Rescue Network visit their website by clicking here.

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Sharks Bay Umbi Diving Village is a Bedouin-owned resort with stunning views and a lovely private beach. It is ideal for divers as everything is onsite including the resort's jetty, dive centre and house reef. The warm hospitality makes for a diving holiday like no other. There is an excellent seafood restaurent and beach bar onsite, and with the enormous diversity of the Sharm El Sheikh dive sites and the surrounding areas of the South Sinai, there really is something for every level of diver to enjoy.

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