Helen T. Yap

A review of the status of Philippine reefs

Abstract Since 1979, the status of Philippine reefs has been periodically updated. While conditions of the reefs during the early surveys were assessed in terms of live coral cover per se, the ‘coral mortality index’ was applied to the sets of data collected during the past 7 yr which may be a better gauge in determining the health of the reefs. Generally, most reefs surveyed are in fair condition. Major destructive factors described are sedimentation and siltation from coastal development and activities inland, illegal and destructive methods of fishing, and overfishing. If the reefs are to continue to provide for the present and future users, the ecological processes that render them productive must be maintained through integrated approaches of coastal area management.

Physiological and ecological aspects of coral transplantation

The growth and mortality of transplants of two species of scleractinian corals, Porites cylindrica Dana and P. rus Forskal (1775), were monitored over 16 months in a reef in the northwestern Philippines. Transplants were in two sizes (nubbin, ∼8 cm in length; and fist-sized, ∼8 cm in diameter) and deployed at two depths (1 and 10 m). Specimens at the shallow depth had more rapid growth than the deeper ones. Light had significant effects on coral growth while temperature, salinity, water motion and sedimentation did not. Smaller corals consistently registered greater percentage increases in size as compared to the larger ones. Small transplants of P. cylindrica showed higher percentage growth rates than those of P. rus. Contrary to expectations, there were no differences in transplant mortality due to size. Over the course of the experiment, mortality was generally confined to the shallow depth. It was brought about either by algal competition or by strong water movement.

The case for restoration of tropical coastal ecosystems

At no time have humans so altered their natural environment than the present. Marine ecosystems have not been spared, and the degradation of coastal habitats has reached severe proportions in many parts of the world. The mere setting aside of areas for protection may not be enough to ensure adequate production and provision of services for a growing global human population. Hence, the active restoration of habitats, in addition to protection and preservation, is probably the more desirable conservation strategy. Accumulated experience over several decades has demonstrated that the rehabilitation or even restoration of damaged coastal ecosystems is feasible. However, the degree of difficulty and expense involved vary, with coral reefs being the most complicated habitats to restore, followed by seagrass beds and then mangrove forests. In ecosystem restoration, a comprehensive strategy based on sound biological and ecological principles, and proven techniques must be developed. A concrete, achievable goal must be articulated. Because of the dynamic nature of ecosystems, and the inability to accurately predict pathways of succession after a community is established through artificial means, subsequent modifications to a project must proceed within a flexible framework of adaptive management. Finally, for restoration efforts to be successful, local communities must participate actively in cooperation with local governments in accordance with the principle of co-management.

Growth of Acropora pulchra

The growth of both undisturbed colonies and transplants of the branching coral Acropora pulchra (Brook) was studied over a 17-month period in the reef of Bolinao, Pangasinan, northern Philippines. Growth rate was monitored using linear measurement techniques. Of the environmental factors measured, both temperature and day length, in the range of natural conditions encountered, correlated negatively with the growth and branching of the undisturbed corals and, to a lesser extent, growth of the transplants. Temperature, in addition, appeared to affect mortality of the transplants significantly. Using various methods of computation of data for the undisturbed colonies, the projected annual growth rate of the species was found to range from 13.1 to 15.8 cm yr-1. Growth rates of the transplants were in general considerably lower.

Metabolic responses of the scleractinian coral Porites cylindrica Dana to water motion. I. Oxygen flux studies

Abstract Nubbins of Porites cylindrica Dana collected from a shallow reef flat in the northwestern Philippines were studied for water motion effects. Specimens were maintained in field and laboratory high (HWM) and low (LWM) water motion setups. The average maintenance times were 93 and 77 days for the field and laboratory study, respectively, which were carried out in tandem. After each maintenance period, oxygen fluxes of the corals were measured with increasing stirring rates in a laboratory flow-through respirometry system under a constant light intensity. Photosynthesis-irradiance (P-I) curves were also determined for the laboratory maintained nubbins as well as for a set of control nubbins which were kept in the collection site for 71 days. In both HWM and LWM corals, maximum rates of net photosynthesis (NP) and respiration (R) were achieved upon increasing stirring rates or turbulence to a certain level, indicating that the boundary layer limiting oxygen diffusion had been reduced to a minimum. The LWM corals attained maximum photosynthetic rates at lower rates of water motion, suggesting greater photosynthetic efficiency at lower levels of turbulence than their HWM counterparts. Profiles of NP and R with increasing stirring rates were consistently depressed for the LWM corals. Significant differences between the HWM and LWM treatments were detected in the NP profiles of the field maintained corals and in the R profiles of the laboratory maintained nubbins. The small yet significant difference in the NP profiles of the field HWM and LWM corals was attributed to the subsaturating irradiance used in the laboratory measurements because P-I curves of the laboratory maintained corals showed a large and significant difference between water motion treatments (HWM > LWM) at higher irradiances. While exhibiting lower photosynthetic rates, LWM corals had proportionally lower respiration rates resulting in P:R values very close to those of the HWM corals. Results suggest that Porites cylindrica is able to maintain its metabolic efficiency despite changes in the water motion regime.

Comparison of coral growth and survival under enclosed, semi-natural conditions and in the field

Two closely related scleractinian coral species, Porites cylindrica and Porites rus, were transplanted to two different locations: the natural environment on the reef flat, and culture tanks on land. The use of tanks enabled the regulation of certain environmental factors, and, hence, the evaluation of specific responses of the corals to these factors. For both species, growth and survival were much better in the field than in the land-based tanks most probably due to unrestricted water circulation. Since the two species were subjected to identical experimental treatments, it was possible to distinguish inherent differences between them in terms of responses to external variables. Porites cylindrica was more susceptible than P. rus to predation by corallivores. Predators, as well as grazers, occurred in significant numbers in the field, but not in the land-based tanks. Porites rus, on the other hand, succumbed more readily to overgrowth by macroalgae which thrived in the culture tanks presumably because of significantly higher nutrient levels and the conspicuous absence of grazers. These results have broader ecological implications because of accelerated environmental changes taking place in present-day reefs due to human impact. Major examples are eutrophication and alterations in water circulation which frequently result in sub-optimal conditions for coral survival and growth.

Growth and survival of coral transplants with and without electrochemical deposition of CaCO3

Abstract This study aims to investigate experimentally the effect of electrochemical deposition of CaCO 3 on linear and girth growth, survival and skeletal structure of Porites cylindrica Dana. Transplanted coral nubbins were subjected to up to 18 V and 4.16 A of direct current underwater to induce the precipitation of dissolved minerals. Naturally growing colonies showed a significant increase in percentage longitudinal growth over the treated and untreated corals. Survival followed a similar trend as the growth rate. Lowest survival rates were found in the untreated nubbins. Phenotypic alterations were observed in the treated nubbins where the basal corallites decreased in size with a concomitant increase in their number per unit area. This was probably due to increased mineral concentration (such as Ca 2+ , Na − , Mg 2+ , CO 3 2− , Cl − , OH − and HCO 3 − ) at the basal region of the nubbins. These alterations were accompanied by a significant increase in girth growth rates of the treated nubbins at their basal regions. The abundance of mineral ions at the basal region thus appeared to be utilized by the numerous small polyps for a lateral increase in size of the nubbins instead of a longitudinal increase.

Surge ammonium uptake of the cultured seaweed, Kappaphycus alvarezii (Doty) doty (Rhodophyta: Gigartinales)

The possibility that the cultured seaweed Kappaphycus alvarezii may demonstrate surge ammonium uptake was studied using the perturbation method. Cultivars of the green morphotype of K. alvarezii were incubated at three different initial NH4+ concentrations (i.e., 10, 20, 30 μM) at the same light intensity. Additional incubations were conducted at 30 μM initial NH4+ concentration in the dark. K. alvarezii were also placed in a 30 μM NH4+-enriched seawater medium for 1 h before incubation at 30 μM initial NH4+ concentration. Levels of enrichment and time had significant effects on ammonium uptake rates. Surge ammonium uptake tended to be higher with higher initial ammonium concentration. Mean uptake rates at 10 μM NH4+ initial concentration were significantly lower compared to other treatments. Higher variability in uptake was noted during the first hour of incubation. Ammonium uptake in the dark was not significantly different from that in light (at 30 μM NH4+ initial concentration). Surge uptake was higher for incubations without additional enrichment than when the alga was additionally exposed to enriched medium before the experiment. On average, surge uptake (VS) occurred within the first 30 min and ranged from 15 to 35 μmol NH4+ g−1 DW h−1. Internally controlled uptake (VI) ranged from 5 to 15 μmol NH4+ g−1 DW h−1 and occurred from 30 min to 6 h after exposure to the nutrient. Externally controlled uptake (VE) was less than 5 μmol NH4+ g−1 DW h−1 and occurred from 6 to 8 h after exposure when the medium was significantly depleted of ammonium (as in 10 and 20 μM NH4+ initial concentrations). K. alvarezii from Danajon Reef, central Philippines thus exhibits surge ammonium uptake and some form of nitrogen limitation. Such a strategy is needed for surviving in environments with low or erratic nutrient supplies.

Skeletal extension rates of Porites cylindrica and Porites (Synaraea) rus after transplantation to two depths

With the increasing degradation of coral reefs worldwide, interest has grown in the possibility of reef rehabilitation using coral transplantation as a tool (Clark and Edwards 1995). More data are clearly needed on the physiology and ecology of the different scleractinian species that are dominant on reefs, particularly in terms of responses to transplantation. Coral species that would be more desirable or useful as seed material (in the form of introduced fragments or colonies) in the restoration of natural reef populations should obviously be able to survive the trauma associated with breakage and relocation, and to be able to respond similarly to naturally established colonies in a new environment. With these considerations in mind, the aims of this experiment were (1) to elucidate the effects of transplantation to two depths on the skeletal extension rate of two species of scleractinian corals, Porites cylindrica and Porites (Synaraea) rus; and (2) to compare growth of transplants with naturally established colonies.

Ammonium and phosphate excretion in three common echinoderms from Philippine coral reefs.

The ammonium and phosphate excretion and oxygen consumption of three species of echinoderms (Tripneustes gratilla, Protoreaster nodosus and Ophiorachna incrassata) commonly encountered in Philippine coral reefs were investigated in relation to time of day (i.e. daytime between 10:00 and 12:00 h vs. nighttime between 22:00 and 24:00 h) and their recent feeding history (i.e. recently-collected vs. short-term starvation for 3+/-1 days). The experiment used whole organism incubations and followed a nested hierarchical design. Ammonium excretion rates were 1447+/-310 nmolg(-1) DWh(-1) (mean+/-S.E., n=24) for T. gratilla, 361+/-33 for O. incrassata and 492+/-38 for P. nodosus. Ammonium excretion differed significantly among species, time of incubation and recent feeding history. Interaction between species and recent feeding history was also significant. The organisms excreted more ammonium during daytime except for starved specimens of O. incrassata. In addition, animals that were starved in the laboratory for a few days had a tendency to excrete more ammonium than recently-collected specimens. Phosphate excretion rates were 25+/-13 nmolg(-1) DWh(-1) for T. gratilla, 10+/-2 for O. incrassata and 4+/-1 for P. nodosus. There were no significant differences in phosphate excretion among the three species of echinoderms, their recent feeding history and time of day. Oxygen consumption rates were 286+/-24 µg O(2)g(-1) DWh(-1) for T. gratilla, 64+/-3 for O. incrassata and 54+/-3 for P. nodosus. Oxygen consumption differed significantly among species and recent feeding history but differed only slightly with time of incubation. There was a significant correlation between oxygen consumption and ammonium excretion (r=0.48, P=0.018), and between oxygen consumption and phosphate excretion (r=0.41, P=0.047) for T. gratilla. The nutrient excretion by tropical echinoderms is another pathway by which inorganic nutrients are regenerated in coral reef communities. However, the quantity of nutrients excreted is dependent on the species of echinoderms, their nutritional status and time of day.