010 Marine Ecology

Ecology Ecology = the study of the interaction of organisms with their environments.

Ecology It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things.

Biotic & Abiotic Factors Competitors Disease Predators Food availability Habitat availability Symbiotic relationships Abiotic Factors pH Temperature Weather conditions Water availability Chemical composition of environment nitrates, phosphates, ammonia, O2, pollution

Ecology The word "ecology" coined from Greek word "oikos", which means "house" or "place to live”.

The Scope of Ecology population growth competition between species symbiotic relationships trophic (=feeding) relationships origin of biological diversity interaction with the physical environment

Energy Flow & Nutrient Cycle

Food Chains Artificial devices to illustrate energy flow from one trophic level to another Trophic Levels: groups of organisms that obtain their energy in a similar manner Food Chains Although the term 'food chain' has entered into common usage, in most ecosystems food chains do not occur. The idea that energy flows along a chain of consecutive links made up of various consumers is unrealistic. As we will see shortly, trophic interactions are considerably more complex than a series of linear steps. Food chains are a useful beginning to illustrate the concept of trophic levels. Trophic levels are a way of identifying what kinds of food an organism uses. Primary producers obtain their energy from the sun or chemical sources and utilize inorganic compounds from the environment to make organic compounds. Herbivores feed on primary producers that utilize the sun for energy Carnivores feed on herbivores and other heterotrophic organisms.

Food Chains Total number of levels in a food chain depends upon locality and number of species Highest trophic levels occupied by adult animals with no predators of their own Secondary Production: total amount of biomass produced in all higher trophic levels Food Chains In food chains, the total number of trophic levels depends upon the location and number of different species. In general, the highest trophic level is occupied by adult animals with no predators of their own. For example, killer whales would occupy the highest trophic level in an antarctic food chain. Secondary production refers to the total amount of animal biomass produced in all trophic levels above the primary producers. That is, it reflects all heterotrophic production.

Nutrients Inorganic nutrients incorporated into cells during photosynthesis - e.g. N, P, C, S Cyclic flow in food chains Decomposers release inorganic forms that become available to autotrophs again Nutrients Inorganic nutrients are incorporated into cells during photosynthesis and chemosynthesis. Examples of important nutrients are nitrogen, phosphorus, carbon and sulfur. The flow of nutrients in a food chain is cyclical. A pool of nutrients resides in a trophic level until animals die or excrete it. Then decomposers can release it in a form that is utilizable by autotrophic organisms.

Energy Non-cyclic, unidirectional flow Losses at each transfer from one trophic level to another - Losses as heat from respiration - Inefficiencies in processing Total energy declines from one transfer to another - Limits number of trophic levels Energy Unlike nutrients, the flow of energy is not cyclical but rather is unidirectional. Energy is captured by primary producers and transferred to higher trophic levels. At each transfer, only a fraction of the energy is passed on and much is lost. These losses are in the form of heat and inefficiencies in processing and assimilating energy. Thus, the total available energy declines as one moves up trophic levels in a food chain. This places a limit on the number of trophic levels that can exist. At some point, there is too little energy available to sustain further transfers.

Energy Flow

Energy Flow through an Ecosystem sun Food Chain Primary Producer Primary Consumer Secondary Consumer Tertiary Consumer zooplankton larval fish phytoplankton fish heat Example Food Chain This simplified food chain illustrates links in a food chain. The chain begins with diatoms which are consumed by herbivorous copepods. The copepods are consumed by carnivorous zooplankton (in this case, chaetognaths) and the chaetognaths are consumed by planktivorous fishes. In a food chain, energy moves in a linear fashion from producers through consumers. heat heat water Nutrients fungi Decomposer

Transfer Efficiencies Efficiency of energy transfer called transfer efficiency Units are energy or biomass Pt = annual production at level t Pt-1 = annual production at t-1 Et = Pt Pt-1 Transfer Efficiencies Only a portion of the energy in one trophic level makes its way to the next. This is called the transfer efficiency. The currency may be energy or biomass.

Transfer Efficiency Example Net primary production = 150 g C/m2/yr Herbivorous copepod production = 25 g C/m2/yr = Pcopepods Et = Pt Pt-1 = 25 = 0.17 Pphytoplankton 150 Transfer Efficiency Example Let's assume that we wish to calculate the transfer efficiency between primary producers and herbivorous copepods. Our currency will be grams of carbon. The annual production of primary producers is 150gC per square meter per year. The annual production of copepods is 25 gC per square meter per year. The transfer efficiency is then 25/150 or about 17%. Typical transfer efficiencies from primary producers to herbivores are about 20% while efficiencies between higher levels are about 10%. Typical transfer efficiency ranges *Level 1-2 ~20% *Levels 2-3, …: ~10%

Energy & Biomass Pyramids 10% efficiency Tertiary consumers 10 J 2nd order carnivores Secondary consumers 100 J 1st order carnivores Primary consumers 1,000 J Deposit feeders, filter feeders, grazers Primary producers 10,000 J algae, seagrass, cyanobacteria, phytoplankton 1,000,000 J sunlight

Energy Use By An Herbivore Feces Growth Cellular Respiration

Food Webs Food chains don’t exist in real ecosystems Almost all organisms are eaten by more than one predator Food webs reflect these multiple and shifting interactions Food Webs Remember that food chains are an artificiality that don't really exist. In reality, the trophic linkages between organisms are much more complicated. Most organisms have more than one predator and the diets of animals shift as they develop. Food webs reflect the complexity of trophic interactions.

Antarctic Food Web

Some Feeding Types Many species don’t fit into convenient categories Algal Grazers and Browsers Suspension Feeding Filter Feeding Deposit Feeding Benthic Animal Predators Plankton Pickers Corallivores Piscivores Omnivores Detritivores Scavengers Parasites Cannibals Ontogenetic dietary shifts Food Webs ... There are many trophic categories that are too complicated to fit into the simple concept of a food chain. Many animals are omnivorous. That means that they consume a wide variety of prey. An omnivore might consume diatoms and crustacean larvae. Thus, it's feeding at trophic levels one and two. Detritivores feed on dead organic matter that can be derived from a wide range of sources at varying trophic levels. During development (ontogeny) animals often shift their diet as they grow larger. Consider a tuna which may begin by feeding on copepods and zooplankton but which progresses to large fish at adulthood. Parasites complicate the picture because they may have a number of different hosts of different trophic status.

Recycling: The Microbial Loop All organisms leak and excrete dissolved organic carbon (DOC) Bacteria can utilize DOC Bacteria abundant in the euphotic zone (~5 million/ml) Numbers controlled by grazing due to nanoplankton Increases food web efficiency The Microbial Loop All organisms leak organic carbon compounds into the water. This organic carbon (DOC) is an important food source that would be a net loss to each trophic level. Bacteria are abundant in seawater and many bacteria are capable of utilizing this DOC. Bacterial numbers are controlled via grazing by nanoplankton (ciliates and flagellates). These small zooplanktors are then consumed by larger zooplankton. In this way, the lost DOC is recycled and returns to the food web.

Microbial Loop Solar Energy CO2 nutrients DOC Phytoplankton Herbivores Planktivores DOC Piscivores Bacteria Nanoplankton (protozoans)

Keystone Species A species whose presence in the community exerts a significant influence on the structure of that community.

Keystone predator hypothesis - predation by certain keystone predators is important in maintaining community diversity.

Paine’s study on Pisaster and blue mussels

Keystone Species Kelp Forests

Food Webs

Keystone Species Algal turf farming by the Pacific Gregory (Stegastes fasciolatus)

An Ecological Mystery An Ecological Mystery Let's take a look at a food web in the north Pacific ocean that has changed substantially in the past decade.

An Ecological Mystery Long-term study of sea otter populations along the Aleutians and Western Alaska 1970s: sea otter populations healthy and expanding 1990s: some populations of sea otters were declining Possibly due to migration rather than mortality 1993: 800km area in Aleutians surveyed - Sea otter population reduced by 50% An Ecological Mystery Sea otters are marine mammals that live in kelp beds along the western coast of North America from Baja Mexico to Alaska. Once hunted to near extinction, their protection has been one of the success stories of conservation. In the 1970's, sea otter populations were healthy and expanding throughout their range. Scientists noted that by the 1990's some populations of sea otters were declining. One possibility was that the animals had moved rather than died. In 1993, an 800 km long section of the Aleutian Islands was surveyed and the results were alarming. The sea otter population had declined by 50%.

Vanishing Sea Otters 1997: surveys repeated Sea otter populations had declines by 90% - 1970: ~53,000 sea otters in survey area - 1997: ~6,000 sea otters Why? - Reproductive failure? - Starvation, pollution disease? Vanishing Sea Otters In 1997 the Aleutian survey was repeated and the results were worse. Sea otter populations had declined by 90%. In 1970, some 53, 000 sea otters lived in the study area. By 1997, that population was down to about 6,000 animals. A number of possible causes were considered. These included reproductive failure, starvation, pollution and disease. The problem with these hypotheses was that there was no evidence of dead otters that might support the idea of some epidemic or source of mortality that would kill many over a wide range.

Cause of the Decline 1991: one researcher observed an orca eating a sea otter Sea lions and seals are normal prey for orcas Clam Lagoon inaccessible to orcas- no decline Decline in usual prey led to a switch to sea otters As few as 4 orcas feeding on otters could account on the impact - Single orca could consume 1,825 otters/year Cause of the Decline In 1991, one scientist noticed an orca (killer whale) eating a sea otter. This was unusual because sea lions and seals are the normal prey for orcas and a small animal such as a sea otter wouldn't provide much nutrition. At one site called Clam Lagoon, populations of otters remained healthy. Interestingly, that site was inaccessible to orcas. It turned out that orcas had indeed been responsible for the decline in otters. A decline in the abundance of their usual prey forced them to switch to otters. Not all the orcas needed to switch to generate the mortality observed along the Aleutians. As few as 4 orcas feeding solely on otters could have produced an impact of the magnitude observed. A single orca could consume about 1,825 otters per year.

This diagram illustrates the cascade that swept through the food web. Declines in oceanic fish due to overfishing and climatic changes led to a reduction in food for sea lions and seals. This forced the orcas to enter into the coastal waters where they consumed sea otters. Sea otters normally feed on sea urchins. Without this control, the urchins increased in abundance. Urchins graze on kelp, particularly on the holdfast and large numbers of urchins damaged kelp forests. The decline in the kelp forests has had an impact on many others species ranging from sea ducks to sea stars.

Ecological Succession The progressive change in the species composition of an ecosystem.

Ecological Succession Climax Stage New Bare Substrate Colonizing Stage Successionist Stage

2 types of succession SECONDARY PRIMARY Growth occurs on newly exposed surfaces where no soil exists Ex. Surfaces of volcanic eruptions Growth occurring after a disturbance changes a community without removing the soil

Primary Succession For example, new land created by a volcanic eruption is colonized by various living organisms

Secondary Succession Disturbances responsible can include cleared and plowed land, burned woodlands

Mount St. Helens prior 1980

Mount St. Helens Sep. 24, 1980 May 18, 1980

Mount St. Helens Fireweed 1980 after eruption 2004 2012

Volcanic eruption creates Succession after Volcanic Eruption What organisms would appear first? How do organisms arrive, i.e., methods for dispersal? Volcanic eruption creates sterile environment Hanauma Bay Tuff Ring (shield volcano)

Mechanisms of Succession Facilitation Early species improve habitat. Ex. Early marine colonists provide a substrate conducive for settling of later arriving species. Inhibition First arrivals take precedence. Competition for space, nutrients and light; allopathic chemicals. Tolerance As resources become scarce due to depletion and competition, species capable of tolerating the lowest resource levels will survive.

r & K refer to parameters in logistic growth equation r & K Selected Species Pioneer species- 1st species to colonize a newly disturbed area r selected high reproductive output r & K refer to parameters in logistic growth equation high growth rate short life span low competitive ability Late successional species K selected low reproductive output higher maternal investment per offspring high competitive ability long life span slow growth rate

Ecological Succession on a Coral Reef

Successional Models and their Impacts Case 1: No Disturbance (Competitive Exclusion Model) Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model) Case 3: Constant Strong Disturbance (Colonial Model)

(Competitive Exclusion Model) Case 1: No Disturbance (Competitive Exclusion Model) As the reef becomes complex, organisms compete for space. Dominant organism outcompetes other species. Occurs in stable environments. Results in low species diversity. Highly protected patch reefs within lagoons or protected bays Deeper water

Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model) Storms and hurricanes allow for other species to move in Dominant species would not be allowed to reach competitive exclusion After each disturbance have a recovery period Area of high diversity

Case 3: Constant Strong Disturbance (Colonial Model) Constant exposure to disturbance Shallow environment High turnover of species r-selected species

Case 3 Near reef crest Case 2 Reef slope beneath reef crest Reef Case 1 Deep reef slope

Ecological Succession on a Coral Reef The Big Island

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Ecological Succession on a Coral Reef

Successional Models and their Impacts