Climate Change Glossary


In the context of climate change, acidification is a decrease in the pH of a solution, such as seawater, due specifically to the incorporation of carbon dioxide (CO2) into the water.  The pH of seawater is typically 7.5-8.4 (reference: a pH of 7.0 indicates a neutral solution and a pH of greater than 7.0 indicates a basic solution).


Adjustment in natural or human systems to a new or changing environment. Adaptation to climate change refers to adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities (IPCC Third Assessment Report Working Group III: Mitigation).

Adaptive Capacity

The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.


A group of aquatic, photosynthetic, eukaryotic organisms ranging from unicellular to multicellular forms, and generally possess chlorophyll but lack true roots, stems and leaves characteristic of terrestrial plants (Biology Online).


A process or impact that is due to human activity.


The measurement of the depth of an ocean or other large body of water (U.S. EPA, 2002a).


Organisms living on or in ocean, sea or lake bottoms – or as in this case, Long Island Sound.


Gas or liquid fuel made from plant material (biomass). Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline.

Carbon Dioxide (CO2)

A gas that is generated through both natural and anthropogenic activities.  When dissolved in water, CO2 and water combine to form carbonic acid, resulting in acidification of seawater.

Chlorophyll a

A green pigment in phytoplankton that transforms ultraviolet (UV) light energy into chemical energy during the process of photosynthesis (U.S. EPA, 2002a).

Climate Driver

The major climate drivers, or forcing phenomenon, that have an effect on Earth’s changing climate. These include greenhouse gases such as carbon dioxide, as well as the tilt and wobble of the earth, sun heat and magnetic variation, ocean circulation, and others.

Climate forcing

A way to measure how substances such as greenhouse gases affect the amount of energy that is absorbed by the atmosphere.  An increase in climate, or radiative, forcing leads to warming, while a decrease produces cooling (U.S. EPA, 2010).


The breakdown of organic matter by bacteria and fungi (U.S. EPA, 2002a).

Dissolved Oxygen (DO)

The concentration of free molecular oxygen that is dissolved in water, usually expressed in milligrams per liter (mg/L), parts per million (ppm), or percent of saturation.  DO allows fish and other life to live in water.  Levels of 5 mg O2/L are optimal for sustaining life; most fish cannot survive prolonged periods at low levels of dissolved oxygen. (U.S. EPA, 2002a).


see Climate Drivers and Ecological Drivers

Ecological Drivers

are climate related factors that cause measurable changes in properties of the physical, chemical and biological environment.  Examples of ecological drivers are factors such as variability in rainfall and available nitrogen.


An ecosystem is a biotic community together with its physical and chemical environment, considered as an integrated unit (USACE, 1999).


A semi-enclosed coastal body of water that has free connection with the open sea and within which sea water is diluted by fresh water from land drainage (U.S. EPA, 2002a).


Overenrichment of a water body by nutrients, such as phosphorus and nitrogen.

Harmful Algal Blooms (HAB)

A small percentage of algal species cause harm to humans and the environment through toxin production or excessive growth.  HABs occur naturally, but human activities that disturb ecosystems in the form of increased nutrient loadings and pollution, food web alterations, introduced species, and water flow modifications have been linked to the increased occurrence of some HABs (Lopez et al, 2008).


According to Long Island Sound Study standards, hypoxia is defined as dissolved oxygen concentrations less than 3.0 mg O2/L.

Impervious surfaces

Are usually constructed surfaces such as roads and roofs that are covered by impenetrable materials. These materials prevent the infiltration of water. Highly compacted soils in urban environments are also considered impervious surfaces.


A representative of the state of certain environmental conditions over a given area and a specified period of time (EPA Indicators Report:

Invasive Species

A species that is: 1) non-native (or alien) to the ecosystem under consideration, and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112).

Land Use

Modification of the natural environment by humans for agricultural, commercial, residential, recreational or other uses.


A set of measurements that quantify results (


Reducing the flow of heat-trapping greenhouse gases into the atmosphere, either by reducing sources of these gases (for example, the burning of fossil fuels for electricity, heat or transport) or enhancing the “sinks” that accumulate and store these gases (such as the oceans, forests and soil) (

Nonpoint source (NPS)

A source of water pollution that is not a “point source” as defined by section 502(14) of the Clean Water Act as any discernible, confined and discrete conveyance.  NPS pollution comes from many diffuse sources and is caused by rainfall or snowmelt moving over and through the ground. As this water, or runoff, moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters and ground waters (US EPA, 2010c).


A variable, measurable property whose value is a determinant of the characteristics of a system (taken directly from:  (US EPA 2011).


Disease-causing organisms (U.S. EPA, 2002a).


Living in or related to open oceans and seas (or here, Long Island Sound).

pH Scale

Scale used to determine the alkaline or acidic nature of a substanceA pH of 1.0 indicates a pure acid and 14 is a purely alkaline (basic) substance.  Pure water is neutral (pH of 7.0) (U.S. EPA, 2002a).


Phytoplankton are microscopic floating photosynthetic organisms in aquatic environments, both freshwater and seawater (Encyclopedia of Earth, 2008).


A capability to anticipate, prepare for, respond to, and recover from significant multi-hazard threats with minimum damage to social well-being, the economy, and the environment.


Amount of salts dissolved in water, usually expressed in parts per thousand (ppt). Within an estuary, salinity levels are referred to as oligohaline (0.5-5.0 ppt), mesohaline (5.0-18.0 ppt), or polyhaline (18.0-30.0 ppt) (U.S. EPA, 2006b).


A measurable variable that is susceptible to some key aspect of climate change and which is being monitored for the appearance of climate change.


From an ecological perspective, a stress is a change that causes a response in a system or population of interest. (taken directly from:; Oz Coasts 2011).


Major physical, chemical and/or biological components of the environment that, when changed by human or other activities, can cause adverse effects on ecosystems and natural resources (Oz Coasts 2011; U.S. EPA 2011).

Submerged Aquatic Vegetation (SAV)

Vascular, rooted aquatic plants, living at or near the water’s surface.


Measure of water clarity (degree to which light is blocked due particulate matter suspended in the water column; U.S. EPA, 2002a).


All land and water areas (such as streams and rivers) that drain toward a given water body, such as an estuary, wetland, or ocean.  Also sometimes called a drainage basin, they are separated from others by a drainage divide (U.S. EPA, 2002a).

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