How does rising atmospheric CO2 affect marine organisms?

Learn how plants respond to higher atmospheric CO2 concentrations

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H

Heat shock proteins
Proteins that are induced by high temperatures that act to prevent or reverse heat-induced damage to other plant proteins.

Heating Degree Day (HDD)
A parameter based on mean daily air temperature that is used to estimate the energy needed to warm indoor air to a comfortable level.  HDDs are calculated by subtracting the mean daily air temperature from a given threshold value (15C, for example).  On days when the mean temperature is above the threshold value, there are no HDDs and heating is not needed.

Heinrich events
Massive discharges of icebergs into the North Atlantic Ocean, six of which have been confirmed to have occurred over the last 75,000 years.

Herbaceous plants
Plants that have soft stems - mostly grasses, forbs, and lichens.

Herbivores
Organisms that eat plants as opposed to animals.

High forest
A silviculture system in which trees are of similar age and experience a high level of competition.

Holocene
The period of time in earth's history, beginning about 12,000 years ago and continuing to the present day, comprising the current or most recent interglacial.

Homoiochlorophyllous desiccation-tolerant plants
Species that retain their chlorophyll and photosynthetic apparatus during desiccation.

Humic substances
These substances arguably compose the most important fraction of total soil organic matter, as they can increase soil water content, mineral retention, and stability, as well as buffer soil pH and immobilize potentially toxic metals away from plants.

Hurricane
A tropical cyclone with winds in excess of 64 knots (74 mph).

Hybrid
The progeny that results from the mating or crossing of two different species or organisms.  In plants, hybrids often display characteristics that are more favorable than those of their parents.

Hydrographic data
Measurements of the physical and dynamical characteristics of a body of water such as a lake, river or ocean current.

Hypdroponics
A system used for growing plants wherein their root systems are submerged in aqueous solutions, as opposed to being anchored in various types of non-aqueous mediums.

Hyphae
A threadlike tubular filament possessed by many fungi that function in nutrient absorption and transfer.

Hypothesis
A supposition or idea about something.  In the scientific realm, it generally relates to physical or chemical interactions among various entities of nature.