MERCER02-14
1
1. Background andObjectives
On October 11, 2013, staff from Constellation Energy Group and the University of Maryland
Center for Environmental Science (UMCES) Chesapeake Biological Laboratory (CBL) met to
discuss an ongoing problem that Calvert Cliffs Nuclear Power Plant (CCNPP) is experiencing
resulting from colonization and growth on intake pipes by the rope grass hydroid (
Garveia
franciscana
) (Torrey 1902). Large colonies of this hydroid form on intake pipes of the CCNPP
cooling water system, potentially reducing flow of cooling waters and periodically but
unpredictably breaking loose, clogging filter screens and impacting pump performance. This
hydroid from the familyBougainvillidae is a common fouling organism and awidely distributed
non-native or invasive species in theChesapeakeBay.
Based on discussions between Constellation and CBL staff, it was agreed that the first step in
addressing this issue would be a review of existing information and options. This report
completes Task 1.1 – A review of the biology, life history and physiological tolerances of
G.
franciscana
, and Task 1.2 –A review of three potential categories of approaches for controlling
or minimizing impacts
G. franciscana
cooling pipe fouling: (a) water treatment, (b) pipe
coatings, and (c) mechanical control. Based on this information, recommendations on additional
experiments, testing and trial applicationswill bemade.
2.
Garveia franciscana
Biology
2.1. Background
Garveia franciscana
(commonly known as the rope grass hydroid) is a colonial marine hydroid
(Cnidaria, Hydrozoa, Anthomedusae, Bougainvilliidae), and a very common sessile organism in
temperate and subtropical estuaries (Thompson 1993). Hydroids are a class of marine
invertebrate, closely related to sea anemones and corals, which are often mistaken as seaweeds
when attached and growing to hard substrates such as rocks and pilings (Figure 1). Some have
branching stems and others just have simple stalks.
a.
b.
Figure 1. Photos of
Garveia franciscana
: a. (Fofonoff et al. 2003) and b. (Zammit
et al. 2013).
The native range of
G. franciscana
is unknown; however, it is suggested that the species has
native populations in both India/Indian Ocean and East Brisbane/Queensland/Brisbane River,
Australasia (Fofonoff et al. 2003). This hydroid exhibits broad tolerances to environmental
