Comprehensive Study Notes on Corals and Marine Ecology in Panama

Introduction to Phylum Cnidaria and Corals

• Taxonomy and Context: The study focuses on Phylum Cnidaria (also known as Coelenterata). This is presented as Class 2 by Professor Carmen I. Lizarraga D.

• Etymology: The word "coral" originates from the Latin term corallium, which translates to "little stone." This naming convention was adopted by 16th-century naturalists because corals possess a rocky structural framework.

• Biological Definition:

  • Corals are primitive marine animals.

  • They are predominantly colonial, although some exceptions exist.

  • A coral colony is composed of hundreds or thousands of individual units known as zooids (pólipos).

Environmental Requirements for Reef Development

• Geographic Distribution: Reefs flourish in waters located at latitudes below $30^{\circ}$ (between the Tropic of Cancer and the Tropic of Capricorn).

• Temperature Thresholds: Development requires a environment where the water temperature never falls below $18^{\circ}C$.

• Regulating Factors: The primary factors governing the development of coral reefs include:

  • Water temperature.

  • Salinity levels.

  • Water clarity (transparency/low turbidity).

  • Low levels of nutrients (oligotrophic conditions).

• Salinity: Defined as the total quantity in grams of solid substances contained in one kilogram of seawater. It is expressed in parts per thousand (ppt).

  • The average salinity of the oceans is approximately $35\,ppt$.

  • This means one kilogram of seawater contains $35\,g$ of dissolved salts.

The Chemical Process of Calcification

• Definition: Calcification is the metabolic process where calcium ions and bicarbonate ions are combined to produce mineral calcium carbonate and protons.

• Chemical Reaction: The process is represented by the following chemical equation:     $Ca^{2+} + HCO_3^{-} \rightarrow CaCO_3 + H^{+}$

• Structural Growth: Through this reaction, corals incorporate the mineral calcium carbonate ($CaCO_3$) into their structures, thereby increasing their size.

• Essential Requirements for Calcification: For this process to occur within the water column, three elements must be present:

  1. Calcium ($Ca^{2+}$).

  2. A source of inorganic carbon (carbonate, bicarbonate, or carbon dioxide).

  3. An adequate pH level.

• Relationship with Salinity: The level of calcium in the water is directly proportional to the level of salinity. As salinity increases, the concentration of calcium ions increases, and vice versa.

Chemical Composition of Seawater and Marine Characteristics

• Seawater Composition: Seawater is a complex chemical solution of minerals derived from the Earth's crust and organic salts from plant and animal remains.

• Major Solid Components (by percentage):

  • Chlorine ($Cl^{-}$): $55.1\%$

  • Sodium ($Na^{+}$): $30.6\%$

  • Sulfate ($SO_4^{2-}$): $7.6\%$

  • Magnesium ($Mg^{2+}$): $3.7\%$

  • Calcium ($Ca^{2+}$): $1.2\%$

  • Potassium ($K^{+}$): $1.1\%$

  • Minor components: Iodine, Silica, and Bromine.

• Specific Compound Concentrations (in $g/dm^3$):

  • Sodium Chloride ($NaCl$): $24\,g/dm^3$

  • Magnesium Chloride ($MgCl_2$): $5\,g/dm^3$

  • Neutral Sodium Sulfate ($Na_2SO_4$): $4\,g/dm^3$

  • Calcium Chloride ($CaCl_2$): $1.1\,g/dm^3$

  • Potassium Chloride ($KCl$): $0.7\,g/dm^3$

  • Sodium Bicarbonate ($NaHCO_3$): $0.2\,g/dm^3$

  • Sodium Bromide ($NaBr$): $0.096\,g/dm^3$

  • Boric Acid ($H_3BO_3$): $0.026\,g/dm^3$

  • Strontium Chloride ($SrCl_2$): $0.024\,g/dm^3$

  • Sodium Fluoride ($NaF$): $0.003\,g/dm^3$

Limiting Factors and Influences on Growth

• Primary Growth Factors:

  • Water quality parameters.

  • Nutrition/Feeding.

  • Illumination (Light levels).

  • Water circulation.

  • Unlimited source of calcium ($Ca$), carbonates ($CO_3$), and magnesium ($Mg$).

• Influence of Marine Currents: A continuous flow of water ensures a continuous flow of nutrients, specifically phytoplankton and zooplankton.

• Limiting Factors for Reefs:

  • Light intensity (for photosynthesis by symbionts).

  • pH levels.

  • Temperature extremes.

  • Salinity variations.

  • Depth of the water column.

  • Sedimentation (which can smother polyps).

Classification and Types of Corals

• Practical Classification Groups: Corals are generally categorized into three groups:

  1. Fire Corals (Corales de fuego).

  2. Stony Corals (Corales pétreos).

  3. Soft Corals (Corales blandos).

• Stony Corals (Order Scleractinia / Madreporaria):

  • Distinguished by their hardness.

  • Polyps have six tentacles (Order Hexacorallia).

  • Skeleton is composed of calcium carbonate ($CaCO_3$).

  • Includes: Actiniaria, Zoanthidea, Scleractinia, and Corallimorpharia.

• Horny/Corny Corals (Order Octocorallia):

  • Distinguished by flexible bodies.

  • Polyps have eight tentacles.

  • Skeletons are composed of chitin and calcareous spicules.

  • Includes: Alcyonacea, Gorgonacea, and Pennatulacea.

Major Types of Coral Reef Formations

• Fringing Reef (Arrecife costero): Connects directly to a coastal shore or is separated by a very shallow channel or lagoon.

• Barrier Reef (Arrecife de barrera): Separated from the mainland coast or an island by a deep channel or lagoon.

• Atoll (Atolón): A roughly circular or continuous reef extending around a lagoon without a central island.

Importance of Coral Reef Ecosystems

• Fisheries and Food Security: Many nations depend on reefs to sustain their fishing industry and food supply.

• Coastal Protection: Reefs protect coastlines from erosion and the impact of waves and storms.

• Economic Impact: They are a significant source of recreation and stimulate tourism.

• Biological Networks: They form critical and complex food webs.

• Science and Commerce: They have identified applications in medicine and commercial products.

Corals of Panama: Geographic Distribution and Species

• Regional Distribution: The most developed reefs are found in the Caribbean (principally San Blas, Bocas del Toro, and Colón). In the Pacific, the most developed reefs are in the Gulf of Chiriquí.

• Key Coral Species in Panama:

  • Porites sp.

  • Diploria sp.: Commonly known as "Brain Coral" (Coral cerebro). Specifically Diploria labyrinthiformis (Grooved Brain Coral).

  • Agaricia sp.: Known as "Lettuce Coral" (Coral lechuga).

  • Millepora sp.: Known as "Fire Coral" (Coral de fuego).

  • Acropora cervicornis: Known as "Staghorn Coral" (Cuerno de ciervo).

  • Acropora palmata: Known as "Elkhorn Coral" (Cuerno de Alce).

  • Gorgonia sp.: Known as "Sea Fan" (Abanico de mar).

  • Thesea galioni: Located in Coiba.

  • Leptogorgia alba.

  • Pacifigorgia rubicunda.

  • Pacifigorgia irene.

  • Heterogorgia cf. verrucosa.

  • Pacifigorgia rubinoffi: Endemic to Coiba.

  • Leptogordia christiae: Found in the Gulf of Chiriquí.

Pacific vs. Caribbean Comparison (2009 Study)

• Study Data: A 2009 study of the Western Pacific of Panama (POP) funded by The Nature Conservancy identified:

  • 75 total coral species: 23 hard corals (scleractinians) and 52 soft corals (octocorals).

• Biodiversity: The coral species distribution in the Panamanian Pacific exceeds that of tropical waters from Mexico to Ecuador.

• Comparative Condition: While the Caribbean slope has roughly 130 species, the report suggests Pacific corals are in better condition.

Coastal Contamination and Environmental Threats

• Sources of Pollution:

  • Natural causes: Floods, hurricanes, tsunamis, earthquakes, parent material, and radioactive material.

  • Anthropogenic (Human) causes: Domestic waste, industrial residues, tourism, agriculture, recreation, mining, fishing, and naval activities.

• Specific Threat Categories in Panama:

  • Incompatible coastal development and urbanism.

  • Solid waste discharge (often non-biodegradable).

  • Contaminant spills and waste water (sewage/black water and gray water).

  • Industrial infrastructure.

  • Incompatible extraction of fauna and subproducts.

  • Vessel traffic.

  • Agricultural and livestock residues (agrochemicals, feces, urine).

  • Mining activity (heavy metals, strong acids/bases, and sedimentation from tailings).

• Waste Water Definitions:

  • Black water (Aguas negras): Water mixed with bodily excretions; contaminated after human use in toilets.

  • Gray water (Aguas grises): Domestic wastewater before mixing with fecal matter (from laundry, cleaning, food scraps). Contains suspended matter like sand, organic matter, fats, and detergents.

The Process and Impact of Ocean Acidification

• Mechanism: Emissions of $CO_2$ from human activities are absorbed by the ocean. Approximately $50\%$ of the $CO_2$ from fossil fuels burned in the last 200 years has been absorbed by the oceans.

• Chemical Chain of Acidification:

  1. Atmospheric $CO_2$ dissolves in sea water ($CO_2 + H_2O$).

  2. This forms Carbonic Acid ($H_2CO_3$).

  3. Carbonic acid dissociates, lowering the pH and increasing the concentration of Hydrogen ions ($H^{+}$).

  4. High $H^{+}$ concentrations react with Carbonate ions ($CO_3^{2-}$), limiting their availability for organisms to form hard parts (shells/skeletons).

• Consequences:

  • Shells become deformed or dissolve.

  • Calcification rates in coral, algae, and phytoplankton slow down.

  • Invasive species like the Lionfish (Pez león) proliferate in the Caribbean, devouring native species as corals die.

  • Kelp algae (thick structures) invade corals due to high acid tolerance.

Global Statistics and Future Outlook

• Coral Bleaching: Stressful changes in temperature (even shifts of $1\text{ to }2^{\circ}C$) or salinity cause corals to expel their symbiotic zooxanthellae. Without these, the white skeleton is revealed through the translucent tissue.

• Historical Mortality: In 1998, $16\%$ of total global coral reefs died due to rising sea temperatures.

• Current Crisis: Approximately $10\%$ of global reefs are currently dead. Around $60\%$ are at risk due to human activities.

• Future Projections: It is estimated that reef destruction could reach $50\%$ by the year 2030.

• Ecological Impact: Critical ecosystems (mangroves, reefs, coastal lagoons) are being altered beyond their capacity for recovery.