Field Trip

Angelea B. Revantad Field Trip Report

Introduction

Philippine diversity in the coastal environment is one of the richest in the world. This environment includes: mangroves which occupies the landward portion of the area, consisting of trees and shrubs; seagrass comprise of grass-like plants, which inhabit the nearshore area; and coral reef. Last May 1, 2018, the different natural habitats which provide coastal protection such as coral reefs, seagrass meadows, and mangrove forests in Nogas Island, Anini-y, Antique were quantified and assessed using a transect line. The three habitats have established a symbiotic interaction with each other increasing their importance in the marine ecosystem. The coral community along with seagrass and mangrove exert a stablishing effect on the environment. Reefs protect coastline from waves allowing mangrove and seagrass communities to develop. Seagrass trap suspended sediments and slow water movement benefitting corals because of the lessened sediment in the water and the large accumulation of sediment also become a substrate for mangrove to colonize. Mangroves trap sediments from upland protecting seagrass and corals. All three communities hold nutrients from being dispersed and lost into the surrounding ocean water (McKenzie LJ, 2003). Methodology

Mangr Mangro ove The transect plot method was used in the assessment for mangroves. The transect line was laid perpendicular to the shore. Each mangrove was identified according to its family, the circumference of the trunk was measured using a tape measure and the height was estimated. The length of the assessment was 55 m off the shore.

Sea Seagra gr ass The Saito and Atobe method was used in assessing the seagrass. A quadrant with the dimension 50 cm by 50 cm was used. A transect line was laid perpendicular pe rpendicular to the shore which was marked using a GPS. The quadrant was placed every 20 m making sure that the seagrass was not covered by quadrants to avoid error. The percent cover cov er of seagrass was assessed using five indices (5 as the highest and 1 as the lowest).

Coral A transect line was laid parallel to the shore. The transected area was recorded using an action camera. The video was assessed in the classroom in every 0.25 m. Each was identified as hard coral (HC), macro algae (MA), dead coral (DC), dead coral with algae (DCA), and sand (S).

Results and discussions

Mangrove Mangroves are higher plants that predominantly grow in the intertidal areas of tropical and subtropical shorelines. The term mangrove refers to the individual plants, whereas mangal refers to the whole community or association dominated by those plants (Calumpong and Menez, 1997 ). To adapt to saline environment, mangroves developed unique features such as pneumatophores, and prop roots. Pneumatophores are shallow roots that spread widely across the substrate that project from the mud which allow the absorption of oxygen. Prop roots are for better anchorage during typhoons. Two of the most common mangroves found in the Philippines are; Rhizophora and Sonneratia. Sonneratia are medium-sized trees with prominent conical pneumatophores. The leaves are simple, opposite, fleshy and broadly ovate to suborbicular. Rhizophora are medium to large trees with prominent prop roots, occurring in deep, soft mud, normally flooded with tides. The outer bark is ridged, dark-brown on the outside. The leaves are simple, elliptic-oblong to sublanceolate, opposite with wedge-shaped base and pointed tip. In the transected area perpendicular to the coast, the recorded data shows that the dominant species is Sonneratia (59%) and 41% is Rhizophora. Tides are a key factor in determining mangrove association and zonation. Growing seaward is Sonneratia with its roots protruding above the sand. Behind this is Rhizophora with extensive prop roots which reduce the tidal currents, cause extensive deposition of mud and silt, and provide surface for attachment or marine organisms (Calumpong and Menez, 1997).

MANGROVES Rhizophora sp.

Sonneratia sp.

41% 59%

Figure 1. Percent Mangroves

The calculated results show that the mean trunk circumference of Sonneratia is 44.11 which is greater than that of Rhizophora which is 25.17. The mean estimate height of Rhizophora is smaller than Sonneratia by at least 1. According to Flora & Fauna Web, Sonneratia is a tree with broad spreading canopy and height that ranges from 5- 20m. While, Rhizophora is a medium to large-sized erect mangrove tree growing up to 30 m and its trunk can reach up to 50 cm in diameter. Table 1. Calculated results for circumference and height

Species Sonneratia sp. Rhizophora sp.

Mean Trunk Circumference 44.11 25.17

Mean Estimate Height 6.68 5.67

Seagrass Seagrass are flowering grass-like plants which are adapted to saline habitats. It is either grass-like or not in gross external morphology. Most seagrass have long, thin strap-like leaves and a monopodial growth form. The plant arises from a creeping underground stem or rhizome. They attach to all types of substrate, occurring ex tensively on soft ones. In terms of economic and ecological importance, the major functions of seagrass beds are summarized by Wood, Odum and Zieman (1969) as: (1) stabilization and holding of bottom sediments; (2) slowing and retardation of water currents; (3) habitat for aquatic organisms; (4) food; (5) source of organic matter. The species that thrive on sand-dominated substrates are of the Syringodium-Cymodocea Halodule association. The most widely distributed species is Thalassia hemprichii, colonizing as far north in Matanes to Malita, Davao (Calumpong, Medalla and Menez, 1985).

Figure 2 below shows the recorded data of seagrass from the shore in Nogas Island. As observed from the first quadrant that there is abundance of seagrass in the nearshore in the area, while in quadrant 2 the amount of seagrass present decreased significantly but eventually increasing seaward. Quadrant 1

Quadrant 2

Quadrant 3

Quadrant 4

Figure 2. Saito and Atobe Assessment of Seagrass

Legend:

Table 2. Calculated percent cover of seagrass in Quadrant 1

Class 5 4 3 2 1 Total Percent Cover

Frequency 4 6 9 6 0

Midpoint 75 37.5 18.75 9.38 3.13

Frequency*Midpoint 300 225 168.75 56.28 0 750.03 30.0012



Frequency 0 5 14 5 1

Midpoint 75 37.5 18.75 9.38 3.13

Frequency*Midpoint 0 187.5 262.5 46.9 3.13 500.03 20.0012




Midpoint 75 37.5 18.75 9.38 3.13

Frequency*Midpoint 150 150 112.5 112.56 3.13 528.19 21.1276




Midpoint 75 37.5 18.75 9.38 3.13

Frequency*Midpoint 750 262.5 131.25 9.38 0 1153. 12 46.1252

The tables above show the calculated percent cover of the quadrants. The first quadrant has a percent cover of 30.0012, while there was a decrease for utmost 10 towards the second quadrant (20.0012), quadrant 3 (21.1276) then an increase towards the quadrant 4 (46.1252). Seagrass beds in the Philippine waters are threatened by the increasing human population which need extra space for settlement, food, waste disposal and recreation. Undocumented thousands of hectares of seagrass beds have been lost because of the reclamation of coastal areas (Calumpong and Menez, 1997).

Corals Cnidarians, also known as coelenterates are arguably the most common and conspicuous invertebrates found in shallow tropical Pacific waters because this phylum includes the many species of corals which build coral reefs (Anderson, 2003). The most abundant are the hard corals (Sclerectinia). The highest generic richness is believed to occur in the coral triangle (including the Philippines). Most of the corals seen are Heliopora sp. (blue coral), Porites sp., and other encrusting, digitate and massive species of corals. Substrate sand, dead coral, and dead coral with algae are also present.

CORAL REEF Hard coral

Macro algae

Dead coral

Dead coral w/ algae

Sand

13% 25% 11%

16% 35%

Figure 3. Coral reef assessment

The result of the coral reef assessment shows that the most dominant species found in the reefs are the macro algae (35%) followed by hard coral (25%), dead coral (16%), sand (13%), then dead coral with algae (11%). Combining the dead coral and dead coral with algae would result to a greater percentage of dead coral compared to that of hard coral. Which means that the coral reefs in the island is degrading. An explanation for this is the presence of Acanthaster planci, also known as the crown of thorns starfish. Crown of thorns starfish prey on nearly all corals but prefer to feed on branching and table corals. However, if the branching corals cover is low, they eat other corals such as Porites or foliose corals (n.d., 2017).

References

Anderson G 2003. The coral animal. Marine Science. Internet| cited 2014 Oct 28. Available from: http://www.marinebio.net/marinescience/04benthon/crani.htm Calumpong H.P., E.G. Menez. 1997. Field Guild to the Common Mangroves, Seagrasses and Algae of the Philippines. Bookmark, Inc. Makati City. Calumpong. H.P., S.G. Medalla and E.G. Menez. 1985. Taxonomy and distribution of seagrasses in the western coast of the Gulf of Davao, southern Philippines. Philippine Journal of Science. Crown of Thorns Starfish. (2017). Retrieved from http://www.reefresilience.org/coralreefs/stressors/predator-outbreaks/crown-of-thorns-starfish/

Flora Fauna Web - Plant Detail - Rhizophora apiculata Blume. (n.d.). Retrieved from https://florafaunaweb.nparks.gov.sg/Special-Pages/plant-detail.aspx?id=3265 Flora Fauna Web - Plant Detail - Sonneratia alba J. Smith. (n.d.). Retrieved from https://florafaunaweb.nparks.gov.sg/Special-Pages/plant-detail.aspx?id=4739 McKenzie LJ, Campbell SJ, Roder CA 2003. Seagrass-watch: manual for mapping & monitoring seagrass resources by community volunteers 2nd edition. PO Box 5396, Cairns QLd 4870 CRC Reef, PO Box 772, Townsville, QLD 4810. 100 pp. Wood, E.J.F., W.E. Odum and J.C. Zieman. 11969. Influence of seagrass on the productivity of coastal lagoons. Memoirs, Symposium International Costeras (UNAM-UNESCO.).

Field Trip

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