Macroalgae vs. Mangrove Growth and Nutrient Uptake
Hypothesis
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Given the fibrous texture, large root system, and solid structural
plant tissues of mangrove plants; they should contain and remove
more nutrients than macroalgae species in the home aquarium.
Introduction
Currently reverse daylight photosynthesis and refugia are
quite poplar. It is common practice to install and utilize
the nutrient uptake properties of macroalgae in these setups.
More recently a push towards the addition of mangroves has
come to fruition. Mangroves are considered to be excellent
for nutrient uptake. In addition they have other beneficial
aspects of macroalgae including: stability (do not dissolve
during reproduction), lack of toxic chemicals, require less
space to grow, provide physical structure for other organisms,
and remove rather than recycle nutrients. Macroalgae also have
a list of benefits over mangroves including: provide a matrix
for micro crustaceans, recycle nutrients, aesthetic appeal,
ease of harvesting, and quick growth rates.
Purpose
The purpose of this study was two fold. First the investigators
wanted to compare the dry weight (representing Nitrogen and
Phosphorus uptake) of mangroves and macroalgae. Second, the
project was designed to make in-exact measurements of nutrients,
with an emphasis on useful comparisons and terminology for
home hobbyists.
Background
Several studies have focused on the limits of algal growth
in reef systems based upon Nitrogen and Phosphorus uptake (Rosenberg
and Ramus 1981, Rosenberg and Ramus 1982, Lapointe et al. 1987,
Littler et al. 1991, Lapointe et al. 1992, Smith & Buddemeier
1992, Fong et al. 1994,). A very noteworthy and important study
in this field analyzed the ratio of Nitrogen and Phosphorus
in algal tissue (Larned 1998). These studies are the basis
for several projects which followed, and were conducted by
this project's author (Blundell 2003). Previous studies in
the captive systems and on reef systems have been difficult
to follow or of little use to home aquarists. On main reason
for this is that studies often use measurements of grams/day
or grams/linear inch or dry weight/square meter which are too
difficult to apply to home aquariums. This project was the
author's attempt to fix this conundrum.
Procedure
The investigators asked for algal donations and mangrove
donations from a local hobbyists club. Donors were then instructed
to provide exactly one handful of algae. While this may sound
scientifically poor, it appears to be a very universal term.
Therefore actual data figures are estimates, but generalizations
can certainly be made.
Algae samples (one handful) and mangrove plants were received.
All samples were simply blotted dry and then weighted. This
measurement is a control step, and is not used in the final
analysis. Then all samples were placed in pre-weighed aluminum
foil pouches. Note- mangrove samples were first cut into parts
dividing them as stems, roots, and leaves. The aluminum foil
pouches were then cooked at 350 F for six hours.
After this time the pouches were allowed to cool and were
then weighed again. This allowed for a calculated measurement
of dry mass. The contents of each pouch were then removed and
weighed separate from the foil pounces (which were also weighted
again as controls). The calculated weights were compared with
actual weights of samples, and were identical within 1 grain.
Tables & Figures
Specimen
Size
Dry weight in grams
Chaetomorpha sp.
One Handful
5.70
Caulerpa serrulata
One Handful
2.59
Mangrove Leaf
One Large Leaf
0.19
Mangrove
Stem (43cm/17in)
8.75
Roots
0.97
Leaves
0.58
Total Plant
10.30
Conclusion
In this study we have found that one handful of Chaetomorpha
sp. and Caulerpa serrulata contain 5.7 grams and
2.59 grams of dry weight mass respectively. One mangrove
plant (of a length of 43cm/17in with six leaves) weighed
10.3 grams of dry weight. If a home aquarist were able to
grow one handful of macroalgae in their sump each month,
this would equal 34.2 grams (for Chaetomorpha sp.)
and 15.54 grams (Caulerpa serrulata). This would correlate
to growing 3 entire mangrove plants and 1.5 mangrove plants
during that time in that aquarium!!! That kind of algal growth
is common, but that kind of mangrove growth is unprecedented.
Therefore our hypothesis was wrong and disproved in this
study. The author's viewpoint following this study is that
mangrove plants may be useful to aquariums but in terms of
nutrient uptake they are far inferior to macroalgae growth.
Acknowledgments
The author would like to thank Adam Haycock, Aime Hancey,
and Jake Pehrson for donating the mangroves and algae for this
project. Appreciation is also owed to Gail Blundell for donating
the measurement equipment. A special word of gratitude is also
owed to the author's wife who tolerated the "wonderful smell" generated
from cooking algae in a kitchen oven.
Authors Information
Adam Blundell M.S. works in Marine Ecology, and in Pathology
for the University of Utah. While not in the lab he is the
president of one of the Nation's largest hobbyist clubs, the
Wasatch Marine Aquarium Society (www.utahreefs.com). He is also Director of The
Aquatic & Terrestrial Research Team, a group which utilizes
research projects to bring together hobbyists and scientists.
His vision is to see this type of collaboration lead to further
advancements in aquarium husbandry. Adam has earned a BS in
Marine Biology and an MS in the Natural Resource and Health
fields. Adam can be found at adamblundell@hotmail.com.
References
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