If in case you are wondering where the these green algaes are coming from then let me share you some info I got from the local residents and some helpful sites.
Green Algae in Boracay
Whether we like it or not, the beautiful white sands in Boracay will be partially covered by these green moss or green algae particularly during February and it will automatically disappear by the end of May.
Back in 1997, Boracay was hit by fecal coliform contamination and research found out that the contamination is from untreated human wastes that drain out to sea but that is entirely not related to green algaes according to local tourism officers.
The algae that bloom along White Beach in the calm season, bright green species of Chaetomorpha, Ulva, and Enteromorpha, are such strong indicators of very high nutrient pollution that they are typically found right around sewage outfalls. Along White Beach they bloom every calm season, but die back in the rough season because waves dilute nutrients to lower levels and wash away the algae and the suspended sediments reduce the light levels. Although the problem appears to have gone away, the impacts will quickly become visible again in the next calm season.
Green Moss in BoracayThese blooms are not new, since long term residents claim that they used to take place seasonally as long as 25 years ago, when there was little development on Boracay. At that time the major sources of nutrients were from groundwater discharges from the wetlands, but as sewage inputs built up, the blooms became larger and longer lasting. Now that all the hotels and houses along White Beach are required to be hooked up to the sewage system (except those who are denied connection because the system is over-loaded), their nutrients flow to the other side of the island instead of flowing onto the White Beach side.
However, the algae blooms along White Beach have not gone away. The seasonal blooms are due to the uncontrolled explosion of population growth in the interior of the island, whose sewage is not connected to the sewage system. Septic tank discharges maintain very high nutrient levels in the groundwater, which are flowing into the sea at every low tide.
It is interesting to note that there is a widespread, but quite false, local misconception that these green algae blooms “turn into sand”. That is completely incorrect, these are soft weedy species that produce no sand at all. The sand is largely produced by a completely different group of algae, Halimeda, and other algae species that make small limestone grains that become beach sand when they die.
These algae live further from the shore, but these “good” algae, which build the beach, are intolerant of high nutrients because they are overgrown and killed by the “bad” algae, whenever the worthless weed algae species are over-fertilized by sewage.
Source – Global Coral Reef Alliance
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